U.S. patent application number 11/630902 was filed with the patent office on 2009-07-02 for refrigerator and operating method of the same.
Invention is credited to Wei Chen, Hengliang Zhang.
Application Number | 20090165496 11/630902 |
Document ID | / |
Family ID | 35783744 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090165496 |
Kind Code |
A1 |
Zhang; Hengliang ; et
al. |
July 2, 2009 |
Refrigerator and operating method of the same
Abstract
When a Stirling refrigerating engine for cooling a refrigerator
starts, an operation is performed such that a gas-phase fluid
flowing through a natural circulation circuit on a high temperature
side attains a temperature higher than that in a normal operation.
More specifically, the Stirling refrigerating engine operates with
a piston drive speed higher than a normal speed, or a fan motor
arranged for a condenser on the high temperature side stops.
Thereby, a gas/liquid coexistent refrigerant in a high temperature
side evaporator attains a pressure higher than a normal pressure.
Thereby, a liquid phase fluid in a forced-circulation circuit on a
high temperature side also attains a pressure higher than a normal
pressure so that bubbles produced in the liquid phase fluid
disappear, and a circulation pump can start.
Inventors: |
Zhang; Hengliang; (Nara,
JP) ; Chen; Wei; (Aichi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
35783744 |
Appl. No.: |
11/630902 |
Filed: |
June 29, 2005 |
PCT Filed: |
June 29, 2005 |
PCT NO: |
PCT/JP05/11907 |
371 Date: |
December 27, 2006 |
Current U.S.
Class: |
62/498 |
Current CPC
Class: |
F25B 9/14 20130101; F25B
2600/13 20130101; Y02B 30/745 20130101; F25D 2317/0682 20130101;
F25B 2500/26 20130101; F25D 2700/14 20130101; Y02B 30/70 20130101;
F25B 2600/111 20130101; Y02B 30/743 20130101; F25D 17/062 20130101;
F25D 11/025 20130101; Y02B 40/32 20130101; F25D 2400/02 20130101;
F25D 29/00 20130101; F25D 21/04 20130101; F25D 23/003 20130101;
Y02B 40/00 20130101; F25B 2700/02 20130101 |
Class at
Publication: |
62/498 |
International
Class: |
F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 12, 2004 |
JP |
2004-204843 |
Claims
1. A refrigerator comprising: a cooling room for accommodating a
target to be cooled; a refrigerating machine having a cold head
generating a cold air for cooling said cooling room and a warm head
releasing heat caused by the generation of said cold air; a liquid
phase circulation circuit connected to said warm head and passing a
liquid phase fluid; a liquid phase circulation pump arranged in
said liquid phase circulation circuit and circulating said liquid
phase fluid; and pressurizing means capable of pressurizing said
liquid phase fluid.
2. A refrigerator comprising: a cooling room for accommodating a
target to be cooled; a refrigerating machine having a cold head
generating a cold air for cooling said cooling room and a warm head
releasing heat caused by the generation of said cold air; a liquid
phase circulation circuit connected to said warm head and passing a
liquid phase fluid; a liquid phase circulation pump arranged in
said liquid phase circulation circuit and circulating said liquid
phase fluid; a circulation circuit connecting said warm head to a
condenser for liquidizing a gas phase fluid vaporized by the heat
provided from said warm head; and pressurizing means capable of
pressurizing said liquid phase fluid.
3. The refrigerator according to claim 1 or 2, wherein said
pressurizing means is configured to perform the pressurizing by
applying heat to said liquid phase fluid and/or said gas phase
fluid from said warm head.
4. The refrigerator according to claim 1 or 2, wherein said
pressurizing means is heating means having a heat source
independent of said warm head and being capable of applying heat to
said gas phase fluid from said heat source.
5. A method of operating a refrigerator including: a cooling room
for accommodating a target to be cooled; a refrigerating machine
having a cold head generating a cold air for cooling said cooling
room and a warm head releasing heat caused by the generation of
said cold air; a liquid phase circulation circuit connected to said
warm head and passing a liquid phase fluid; a liquid phase
circulation pump arranged in said liquid phase circulation circuit
and circulating said liquid phase fluid; and a circulation circuit
connecting said warm head to a condenser for liquidizing a gas
phase fluid vaporized by the heat provided from said warm head,
wherein said liquid phase fluid is pressurized by applying a
pressure higher than a pressure applied in a normal operation to
said gas phase fluid after the start of the operation of said
refrigerator until said liquid phase circulation pump appropriately
circulates said liquid phase fluid.
6. A refrigerator comprising: a cooling room for accommodating a
target to be cooled; a refrigerating machine having a cold head
generating a cold air for cooling said cooling room and a warm head
releasing heat caused by the generation of said cold air; a liquid
phase circulation circuit connected to said warm head and passing a
liquid phase fluid; a liquid phase circulation pump arranged in
said liquid phase circulation circuit and circulating said liquid
phase fluid; a circulation circuit connecting said warm head to a
condenser for liquidizing a gas phase fluid vaporized by the heat
provided from said warm head; and a control device controlling said
refrigerating machine, wherein said control device executes control
of performing a high-speed operation of a piston of said
refrigerating machine or control of increasing a stroke of a piston
of said refrigerating machine such that said warm head of said
refrigerating machine attains a temperature higher than that in a
normal operation after the start of operation of said refrigerator
until said liquid phase circulation pump appropriately circulates
said liquid phase fluid.
7. A refrigerator comprising: a cooling room for accommodating a
target to be cooled; a refrigerating machine having a cold head
generating a cold air for cooling said cooling room and a warm head
releasing heat caused by the generation of said cold air; a liquid
phase circulation circuit connected to said warm head and passing a
liquid phase fluid; a liquid phase circulation pump arranged in
said liquid phase circulation circuit (60) and circulating said
liquid phase fluid; and a control device controlling said
refrigerating machine and said liquid phase circulation circuit,
wherein said control device starts an operation of said liquid
phase circulation pump or increases the output of said liquid phase
circulation pump on condition that a predetermined time has elapsed
after said refrigerating machine started an operation.
8. A refrigerator comprising: a cooling room for accommodating a
target to be cooled; a refrigerating machine having a cold head
generating a cold air for cooling said cooling room and a warm head
releasing heat caused by the generation of said cold air; a dew
formation preventing pipe arranged along an inner surface of a
casing, connected to said warm head and passing a liquid phase
fluid; a liquid phase circulation pump arranged in said liquid
phase circulation circuit including said dew formation preventing
pipe, and circulating said liquid phase fluid; a control device
controlling said refrigerating machine and said liquid phase
circulation pump; and a temperature sensor measuring a temperature
of the surface of said casing or a temperature of said liquid phase
circulation pipe, wherein said control device starts an operation
of said liquid phase circulation pump or increases the output of
said liquid phase circulation pump on condition that the
temperature sensed by said temperature sensor lowered.
9. A refrigerator comprising: a cooling room for accommodating a
target to be cooled; a refrigerating machine having a cold head
generating a cold air for cooling said cooling room and a warm head
releasing heat caused by the generation of said cold air; a liquid
phase circulation circuit connected to said warm head and passing a
liquid phase fluid; a liquid phase circulation pump arranged in
said liquid phase circulation circuit and circulating said liquid
phase fluid; a radiator for lowering a temperature of said warm
head; a radiator fan arranged near said radiator; and a control
device controlling said refrigerating machine, said liquid phase
circulation pump and said radiator fan, wherein before said liquid
phase circulation pump starts after starting said refrigerating
machine, said control device stops said radiator fan or drives said
radiator fan with a power smaller than that used after starting
said liquid phase circulation pump.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigerator having a
cooling space for cooling stored goods as well as an operating
method of the same.
BACKGROUND ART
[0002] General refrigerators have widely employed vapor compression
refrigerating engines. The vapor compression refrigerating engine
utilizes condensation and evaporation of a flon gas to achieve a
low temperature. Since the flon gas has neither flammability nor
explosibility, and has low corrosivity, it can be used very readily
as a refrigerant. However, the flon gas has a high chemical
stability. Therefore, when the flon gas is released into an
atmosphere, it reaches the stratosphere to destroy the ozone layer.
In recent years, therefore, specified flon (i.e.,
chlorofluorocarbon) and alternative flon have been used, and the
production of the flon gas has been restricted on a worldwide
basis.
[0003] In recent years, therefore, attention has been given to a
Stirling refrigerating engine as a refrigeration technique that can
be substituted for the vapor compression refrigerating engine using
the flon gas as the refrigerant. The Stirling refrigerating engine
is configured to reciprocate a piston and a displacer with an
arbitrary phase difference by an external power such as a motor.
This operation repetitively compresses and expands a working
medium. Consequently, a cold head and a warm head are formed. The
cold head achieves a low temperature.
[0004] The Stirling refrigerating engine can use, as the working
medium, a gas of helium, hydrogen, nitrogen or the like that does
not adversely affect the global environment.
[0005] Patent Document 2: Japanese Patent Laying-Open No.
11-166784
[0006] Patent Document 3: Japanese Patent Laying-Open No.
11-211325
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0007] In a refrigerator provided with the Stirling refrigerating
engine described above, the cold head takes the heat from an inner
space of the refrigerator, and the warm head releases the heat as
waste heat so that the inner space can be cooled without using the
flon gas.
[0008] However, the refrigerator provided with the Stirling
refrigerating engine suffers from a problem similar to that of the
conventional refrigerators. More specifically, the foregoing
refrigerator suffers from a problem that dews are formed on
portions (e.g., a portion around a door packing and an outer wall
surface of the refrigerator) that are cooled to a lower temperature
than a surrounding environment by an inner cold air when the
humidity in the surrounding environment is high.
[0009] Such a refrigerator is already proposed that prevents the
dew formation by an electric heater heating portions on which the
dew formation may occur. However, this structure suffers from a
problem of increase in electric power consumption.
[0010] For overcoming the above problems, the inventors and others
have made study of a refrigerator that can prevent formation of
dews on the outer wall, and can perform drain processing. This
refrigerator is configured such that a liquid portion of a
refrigerant used for cooling a warm head of a Stirling
refrigerating engine is forcedly led to a dew formation preventing
pipe arranged near an outer wall or a drain processing pipe
arranged at a lower portion of the refrigerator.
[0011] The above dew formation preventing pipe is filled with a
liquid phase fluid such as water. Therefore, a gas phase for
externally releasing a heat and a liquid phase for preventing dew
formation are present in a two-phase state. A circulation pump is
used for forcedly circulating the liquid phase fluid.
[0012] In the above forced circulation, when a surrounding
temperature rises when a circulation pump stops for a predetermined
time, the temperature of the liquid phase fluid also rises with it.
This may gasify a part of the liquid phase fluid remaining in the
dew formation preventing pipe. Bubbles generated by gasifying the
liquid phase fluid remain in the liquid phase dew formation
preventing pipe and/or in the circulation pump. This results in a
problem that the circulation pump cannot appropriately circulate
the liquid phase fluid.
[0013] The invention has been made in view of the above problems,
and it is an object of the invention to provide a refrigerator and
an operating method thereof that can eliminate bubbles formed in a
liquid phase dew formation preventing pipe when the refrigerator
stops its operation for a long time, and thereby can overcome the
problem that a liquid phase circulation pump cannot appropriately
circulate the liquid phase fluid during the operation of the
refrigerator.
Means for Solving the Problems
[0014] A refrigerator according to the invention is as follows:
[0015] A refrigerator includes a cooling room for accommodating a
target to be cooled; a refrigerating machine having a cold head
generating a cold air for cooling the cooling room and a warm head
releasing heat caused by the generation of the cold air; a liquid
phase circulation circuit connected to the warm head and passing a
liquid phase fluid; a liquid phase circulation pump arranged in the
liquid phase circulation circuit and circulating the liquid phase
fluid; and pressurizing means capable of pressurizing the liquid
phase fluid.
[0016] According to this structure, the pressurizing of the liquid
phase fluid by the pressurizing means eliminates bubbles that
appeared in the liquid phase fluid when the operation of the
refrigerator stops for a long time. Consequently, such a problem is
prevented that the liquid phase circulation pump runs idle, and the
liquid phase fluid does not circulate through the liquid phase
circulation circuit when the operation of the refrigerator
starts.
[0017] The refrigerator may include a circulation circuit
connecting the warm head to a condenser for liquidizing a gas phase
fluid vaporized by the heat provided from the warm head.
[0018] In an operation method of the invention, the refrigerator
described above applies a high pressure higher than a pressure
applied in a normal operation to the gas phase fluid after the
start of the operation until the liquid phase circulation pump
appropriately circulates the liquid phase fluid.
[0019] In the above method, the pressurizing of the liquid phase
fluid eliminates the bubbles that occur in the liquid phase fluid
when the operation of the refrigerator stops for a long time.
Consequently, such a problem is prevented that the liquid phase
circulation pump runs idle, and the liquid phase fluid does not
circulate through the liquid phase circulation circuit when the
operation of the refrigerator starts.
[0020] The foregoing high pressure may be produced by operating the
refrigerating machine to raise the temperature of the warm head
above the temperature in a normal operation. The foregoing high
pressure may be produced by operating the heating means arranged
independently of the warm head to raise the temperature of the gas
phase fluid above a normal temperature.
[0021] For executing the above method, the refrigerator may include
heating means arranged in the circulation circuit and capable of
pressurizing the gas phase fluid to apply a pressure to the liquid
phase fluid through a gas-liquid separator. This pressurizing means
may be achieved by controlling the warm head to attain a
temperature higher than that in the normal operation, and may also
be achieved by heating means that has a heat source independent of
the warm head and can apply heat to the liquid phase fluid and/or
the gas phase fluid.
[0022] Further, the refrigerator includes a control device
controlling the refrigerating machine, and the control device
executes control of performing a high-speed operation of a piston
of the refrigerating machine or control of increasing a stroke of a
piston of the refrigerating machine such that the warm head of the
refrigerating machine attains a temperature higher than that in a
normal operation after the start of operation of the refrigerator
until the liquid phase circulation pump appropriately circulates
the liquid phase fluid.
[0023] According to another aspect of the invention, a refrigerator
includes a cooling room for accommodating a target to be cooled; a
refrigerating machine having a cold head generating a cold air for
cooling the cooling room and a warm head releasing heat caused by
the generation of the cold air; a liquid phase circulation circuit
connected to the warm head and passing a liquid phase fluid; a
liquid phase circulation pump arranged in the liquid phase
circulation circuit and circulating the liquid phase fluid; and a
control device controlling the refrigerating machine and the liquid
phase circulation pump.
[0024] In the above structure, the control device may start the
operation of the liquid phase circulation pump on condition that a
predetermined time has elapsed after the refrigerating machine
started the operation. Thereby, during a period of the
predetermined time, a pressure is applied to the liquid phase fluid
owing to the rising of temperature of the warm head of the
refrigerating machine so that the liquid phase fluid pressurizes
bubbles. Consequently, the bubbles remaining in the liquid phase
circulation circuit can be eliminated. Thereafter, the liquid phase
circulation pump starts. Accordingly, it is possible to suppress
generation of noises caused by the bubble elimination that occurs
in the liquid phase circulation circuit due to the rapid start of
the circulation pump.
[0025] In the above structure, the control device may increase the
output of the liquid phase circulation pump on condition that a
predetermined time has elapsed after the refrigerating machine
started the operation, and thereby can reduce a flow velocity of
the liquid phase fluid circulating through the liquid phase
circulation circuit immediately after the start of the
refrigerating machine until the normal operation is performed.
Consequently, it is possible to reduce noises caused by the bubble
elimination that occurs in the liquid phase circulation circuit due
to the rapid start of the circulation pump.
[0026] According to still another aspect of the invention, a
refrigerator includes a cooling room for accommodating a target to
be cooled; a refrigerating machine having a cold head generating a
cold air for cooling the cooling room and a warm head releasing
heat caused by the generation of the cold air; a liquid phase
circulation circuit arranged along an inner surface of a casing,
connected to the warm head and passing a liquid phase fluid; a
liquid phase circulation pump arranged in the liquid phase
circulation circuit and circulating the liquid phase fluid; a
control device controlling the refrigerating machine and the liquid
phase circulation pump and; and a temperature sensor measuring a
temperature of the surface of the casing or a temperature of the
liquid phase circulation circuit. The control device starts the
liquid phase circulation pump, or increases the output of the
liquid phase circulation pump on condition that the temperature
sensed by the temperature sensor lowered.
[0027] According to the above structure, the liquid phase
circulation pump can start after the temperature of the liquid
phase fluid lowers and the bubbles in the liquid phase circulation
circuit disappear owing to the condensation. Therefore, it is
possible to suppress generation of noises caused by the bubble
elimination that occurs due to the rapid start of the circulation
pump.
[0028] It is desirable that the foregoing refrigerator further
includes a humidity sensor measuring a humidity near a
predetermined position. It is also desirable that the control
device decreases an output of the liquid phase circulation pump
from the current output, or stops the circulation pump when the
humidity measured by the humidity sensor attains the predetermined
value or more.
[0029] According to the above structure, the temperature of the
liquid phase fluid in the circulation pipe rises with the
temperature of the warm head, and therefore a dew point of an
atmosphere around the liquid phase circulation circuit rises so
that dew formation near the liquid phase circulation circuit can be
suppressed.
[0030] According to yet another aspect of the invention, a
refrigerator includes a cooling room for accommodating a target to
be cooled; a refrigerating machine having a cold head generating a
cold air for cooling the cooling room and a warm head releasing
heat caused by the generation of the cold air; a liquid phase
circulation circuit connected to the warm head and passing a liquid
phase fluid; a liquid phase circulation pump arranged in the liquid
phase circulation circuit and circulating the liquid phase fluid; a
radiator for lowering a temperature of the warm head; a radiator
fan arranged near the radiator; and a control device controlling
the refrigerating machine, the liquid phase circulation pump and
the radiator fan. Before the liquid phase circulation pump starts
after starting the refrigerating machine, the control device stops
the radiator fan or drives the radiator fan with a power smaller
than that used after starting the liquid phase circulation
pump.
[0031] According to the above structure, the rising of the
temperature of the warm head can raise the temperature of the
liquid phase fluid before the start of the liquid phase circulation
pump, as compared with the operation after the start of the liquid
phase circulation pump. Thereby, the pressure of the liquid phase
fluid eliminates bubbles in the liquid phase circulation pump.
Thereafter, the circulation pump starts. Consequently, it is
possible to suppress generation of noises caused by the elimination
of the bubbles in the liquid phase circulation pump.
EFFECTS OF THE INVENTION
[0032] The invention can eliminate the bubbles that occur in the
liquid phase fluid when the operation of the refrigerator stops for
a long time. Consequently, such a problem is prevented that the
liquid phase circulation pump runs idle, and the liquid phase fluid
does not circulate through the liquid phase circulation circuit
when the operation of the refrigerator starts.
[0033] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a cross section showing a schematic structure of a
refrigerator of an embodiment.
[0035] FIG. 2 shows a structure of piping of the refrigerator of
the embodiment.
[0036] FIG. 3 is a block diagram for illustrating a control
device.
[0037] FIG. 4 illustrates a gas-liquid separator arranged around a
cold head.
[0038] FIG. 5 illustrates an operation temperature of a circulation
pump during an operation in a refrigerator operation method of the
embodiment.
[0039] FIG. 6 is a flowchart illustrating start processing of the
refrigerator of the first embodiment.
[0040] FIG. 7 illustrates a refrigerator provided with heating
means different from a warm head of the refrigerator.
[0041] FIG. 8 is a flowchart illustrating start processing of a
second embodiment.
[0042] FIG. 9 is a flowchart illustrating start processing of a
third embodiment.
DESCRIPTION OF THE REFERENCE SIGNS
[0043] 1 refrigerator, 10 housing, 11, 12 and 13 cooling room, 14,
15 and 16 heat-insulating door, 17 packing, 18 shelf, 19 machine
room, 20 duct, 21 cold air outlet, 22 fan, 30 Stirling
refrigerating engine, 40 low temperature side circulation circuit,
41 low temperature side condenser, 42 low temperature side
evaporator, 50 high temperature side natural circulation circuit,
51 high temperature side evaporator, 52 high temperature side
condenser, 60 high temperature side forced circulation circuit, 61
circulation pump, 62, 63 and 64 dew formation preventing pipe, 70
electric heater, 80 dew formation sensing portion, 81 wall surface
humidity sensor, 82 wall surface temperature sensor, 90 control
device, 110 radiator fan
BEST MODES FOR CARRYING OUT THE INVENTION
[0044] Embodiments of the invention will now be described with
reference to the drawings.
First Embodiment
[0045] FIG. 1 is a cross section showing a schematic structure of a
refrigerator of this embodiment. FIG. 2 shows a piping structure of
the refrigerator of this embodiment. A refrigerator 1 is aimed at
food storage, and includes a housing 10 of a heat-insulating
structure. Three cooling rooms or compartments 11, 12 and 13 are
formed at different levels in housing 10, respectively.
[0046] Cooling rooms 11, 12 and 13 have openings on a front side
(left side in FIG. 1) of housing 10, respectively. These openings
are closed by openable heat-insulating doors 14, 15 and 16,
respectively. Heat-insulating doors 14, 15 and 16 are provided at
their rear surfaces with packings 17 surrounding the openings of
cooling rooms 11, 12 and 13, respectively. Shelves 18 suitable for
types of foods to be stored are appropriately arranged in cooling
rooms 11, 12 and 13.
[0047] A cooling system and a heat radiating system that include a
Stirling refrigerating engine 30 as a main component are arranged
over upper, rear and lower surfaces of housing 10. A machine room
19 is arranged at a corner between the upper and rear surfaces of
housing 10, and Stirling refrigerating engine 30 is arranged in
machine room 19. A part of Stirling refrigerating engine 30 forms a
cold head during an operation. A wall surface temperature sensor 82
and a wall surface humidity sensor 81 are arranged in the wall on
the rear side (right side in FIG. 1) of the cooling rooms. Wall
surface temperature sensor 82 can measure the temperature of a
portion neighboring to the rear surface of the cooling room and
also neighboring to a dew formation preventing pipe 62 to be
described later. Wall surface humidity sensor 81 can measure the
humidity of a portion neighboring to the rear surface of the
cooling room and also neighboring to dew formation preventing pipe
62 to be described later. Information obtained by wall surface
temperature sensor 82 and wall surface humidity sensor 81 is
transferred via signal lines to a control device 90 to be described
later.
[0048] A low temperature side condenser 41 is attached to the
foregoing cold head. A low temperature side evaporator 42 is
arranged on a rear side of cooling room 13. Low temperature side
condenser 41 and low temperature side evaporator 42 are connected
together via a refrigerant pipe, and both form a low temperature
side circulation circuit 40. Low temperature side circulation
circuit 40 is filled with a natural medium such as CO.sub.2, which
transfers cold by low temperature side evaporator 42 and low
temperature side condenser 41.
[0049] A duct 20 is arranged within housing 10 for distributing a
cold air obtained by low temperature side evaporator 42 to cooling
rooms 11, 12 and 13. Duct 20 is provided at appropriate positions
with cold air outlets 21 communicating with cooling rooms 11, 12
and 13. Blowers or fans 22 are arranged inside duct 20 for forcedly
discharging the cold air.
[0050] Although not shown, a duct of collecting the air from
cooling rooms 11, 12 and 13 is arranged inside housing 10. This
duct has an opening located under low temperature side evaporator
42, and the air to be cooled is supplied to low temperature side
evaporator 42 as indicated by an arrow B of broken line in FIG.
1.
[0051] Another part of Stirling refrigerating engine 30 forms a
warm head when it operates. A high temperature side evaporator
(warm head) 51 is attached to the warm head. A temperature sensor
55 is attached to high temperature side evaporator 51 as shown in
FIG. 2. A high temperature side condenser 52 releasing the heat to
an outside environment as well as a radiator fan 110 are arranged
on an upper surface of housing 10 (see FIG. 1). High temperature
side evaporator (warm head) 51 and high temperature side condenser
52 are connected together via refrigerant piping to form a high
temperature side natural circulation circuit 50. Radiator fan 110
rotates to form an air flow, which promotes heat exchange between
high temperature side condenser 52 and the outside air.
[0052] High temperature side natural circulation circuit 50 is
filled with a natural medium of water (including aqueous solution)
or hydrocarbon, and the natural medium naturally circulates through
high temperature side natural circulation circuit 50.
[0053] High temperature side evaporator (warm head) 51 is also
connected to a high temperature side forced circulation circuit 60.
High temperature side forced circulation circuit 60 has a
circulation pump 61 forcedly circulating the refrigerant, and also
has pipes 62, 63 and 64 for preventing dew formation. The
refrigerant pipe that forms dew formation preventing pipes 62, 63
and 64 is partially located in the openings of cooling rooms 11, 12
and 13.
[0054] The heat of the refrigerant is applied to the vicinities of
the openings where the dews are likely to occur (i.e., to the
portions near the contact portion between packing 17 and housing
10, i.e., the boundary region between the outer and inner spaces),
and thereby the dew formation is prevented. An electric heater 70
that can be energized to generate heat is attached to a portion
where the dew formation may occur but high temperature side forced
circulation circuit 60 cannot be arranged due to a reason, e.g.,
relating to manufacturing.
[0055] Description will now be given on the operation of
refrigerator 1 having the above structure. When Stirling
refrigerating engine 30 is driven in refrigerator 1 having the
above structure, the temperature of the cold head lowers.
Therefore, low temperature side condenser 41 is cooled to condense
the refrigerant kept therein.
[0056] The refrigerant condensed by low temperature side condenser
41 flows into low temperature side evaporator 42 through low
temperature side circulation circuit 40. The refrigerant flowing
into low temperature side evaporator 42 is evaporated by the heat
of the air flowing outside low temperature side evaporator 42, and
lowers the surface temperature of low temperature side evaporator
42.
[0057] Therefore, the air passing by low temperature side
evaporator 42 becomes cold, and flows into cooling rooms 11, 12 and
13 through cold air outlets 21 of duct 20 so that the temperatures
of cooling rooms 11, 12 and 13 lower. Thereafter, the air in
cooling rooms 11, 12 and 13 returns to the vicinity of low
temperature side evaporator 42 through the duct (not shown) owing
to the air flow caused by the rotation of fans 22.
[0058] The refrigerant evaporated by low temperature side
evaporator 42 returns to low temperature side condenser 41 via low
temperature side circulation circuit 40, which condenses the
refrigerant by taking the heat. The heat exchange operation
described above is repeated.
[0059] As illustrated in FIG. 2, when the heat caused by the
operation of Stirling refrigerating engine 30 and the heat
collected from the inside of the refrigerator by the warm head are
released as waste heat from the warm heat. Therefore, high
temperature side evaporator (warm head) 51 is heated to evaporate
the refrigerant flowing therein.
[0060] The refrigerant that is evaporated by high temperature side
evaporator (warm head) 51 and is in the gas phase state flows
through high temperature side natural circulation circuit 50 into
high temperature side condenser 52 arranged in an upper position.
The air that is supplied by radiator fan 110 from the outside into
high temperature side condenser 52 takes the heat from the
refrigerant flowing into high temperature side condenser 52, and
thereby condenses it. The refrigerant condensed by high temperature
side condenser 52 returns to high temperature side evaporator (warm
head) 51 via high temperature side natural circulation circuit 50,
and receives the heat to evaporate again. The foregoing heat
exchange operation is repeated.
[0061] The liquid phase refrigerant contained in the refrigerant
that is saturated inside high temperature side evaporator (warm
head) 51 is forcedly circulated by circulation pump 61 through high
temperature side forced circulation circuit 60, and is supplied
into dew formation preventing pipes 62, 63 and 64. Therefore, the
refrigerant thus supplied heats the portions near the openings of
cooling rooms 11, 12 and 13 by its heat.
[0062] Owing to the above structure, the portions near the
openings, i.e., the portions where the dews are liable to occur can
be kept at a temperature higher than a dew point without requiring
a wasteful electric power, and the dew formation can be prevented.
There are portions where the dew may be formed but high temperature
side forced circulation circuit 60 cannot be arranged. When
electric heater 70 is energized, it can keep such portions at a
temperature higher than the dew point, and thereby can prevent the
dew formation thereon.
[0063] As shown in FIG. 3, refrigerator 1 of this embodiment has a
dew formation detecting portion 80 that determines, based on the
temperature and humidity of the ambient air, the degree of
possibility of the dew formation at the vicinities of the openings,
and also has control device 90 that controls radiator fan 110,
circulation pump 61 and electric heater 70 based on a result of the
determination by dew formation detecting portion 80.
[0064] This control device is configured to control a circulation
rate of the refrigerant in high temperature side forced circulation
circuit 60 and a quantity of the heat released from high
temperature side natural circulation circuit 50 according to the
degree of possibility of the dew formation. Further, control device
90 is supplied with a signal indicating the temperature measured by
temperature sensor 55 that is employed for measuring the
temperature of high temperature side evaporator (warm head) 51.
Control device 90 is configured to control the operation of
Stirling refrigerating engine 30 based on the signal thus
supplied.
[0065] More specifically, when control device 90 determines based
on the result of detection of dew formation detecting portion 80
that the possibility of the dew formation near the opening is high,
it starts the operation of circulation pump 61 and the energizing
of electric heater 70. When control device 90 determines that the
possibility of the dew formation is low, it stops the operation of
circulation pump 61 and the energizing of electric heater 70.
[0066] Owing to the above structure, unnecessary heating is not
effected on the outer wall surface of the refrigerator when the
possibility of dew formation near the opening is low. Therefore, a
thermal load on the inside of the refrigerator can be suppressed,
and the power consumption can be reduced. For example, when the
ambient temperature is high and the ambient humidity is low, the
load required for the cooling increases, and the warm head attains
a high temperature.
[0067] However, the foregoing control reduces the circulation
quantity of the refrigerant in high temperature side forced
circulation circuit 60. Consequently, the dew formation can be
appropriately prevented without heating the outer wall surface of
the refrigerator. The employment of the foregoing structure reduces
the operation time of circulation pump 61, i.e., a machine element
that is relatively liable to go wrong, and therefore can contribute
to improvement of the reliability of the refrigerator.
[0068] When control device 90 determines based on the result of
detection of dew formation detecting portion 80 that the
possibility of the dew formation near the opening is high, it
performs another control, simultaneously with the foregoing
control, to reduce the quantity of air supplied from radiator fan
110 (i.e., the quantity of released heat of high temperature side
natural circulation circuit 50), and to cause a difference of a
predetermined value or more between the surface temperature of the
warm head and the ambient temperature. The temperature difference
of the predetermined value or more was obtained in advance by
experiments so that the refrigerant flowing through dew formation
preventing pipes 62, 63 and 64 may attain the temperature equal to
or higher than the ambient temperature.
[0069] Owing to the above structure, even when the load on Stirling
refrigerating engine 30 is small (e.g., when an ambient temperature
is low and an ambient humidity is high), the cooling temperature of
high temperature side forced circulation circuit 60 is maintained
at a predetermined value or more. Consequently, dew formation
preventing pipes 62, 63 and 64 can always function.
[0070] As shown in FIGS. 2 and 3, it is desirable that dew
formation detecting portion 80 has wall surface humidity sensor 81
that measures wall surface humidity at the position (e.g., around
dew formation preventing pipes 62, 63 and 64) where the dew
formation is liable to occur to a relatively high extent. In this
structure, it is desirable that control device 90 determines that
the possibility of dew formation is high when the relative humidity
is, e.g., 90% or more, and determines that the possibility of dew
formation is low when the relative humidity is lower than 90%.
[0071] Owing to the above structure, control device 90 can directly
determine the possibility of dew formation according to the
relative humidity near the outer wall surface of the refrigerator.
Consequently, the dew formation can be quickly detected by the
simple structure.
[0072] Wall surface temperature sensor 82 and wall surface humidity
sensor 81 provide the temperature information and humidity
information obtained at the vicinity of dew formation preventing
pipe 62 to control device 90. Based on the temperature information
and the humidity information, control device 90 can control
radiator fan 110, electric heater 70, circulation pump 61 and
Stirling refrigerating engine 30.
[0073] Referring to FIGS. 4 to 6, description will now be given on
a manner of pressurizing a gas phase fluid for eliminating bubbles
that occurred in the liquid phase fluid in the dew formation
preventing pipes according to the embodiment.
[0074] As can be seen from FIG. 4, a liquid phase is present on the
lower side of high temperature side evaporator 51 of the
refrigerator already described, and a gas phase is present on the
upper side so that high temperature side evaporator 51 functions as
a gas-liquid separator. Therefore, bubbles generated on the liquid
phase side generally move upward and are discharged to the gas
phase side. Consequently, a state where no gas (or substantially no
gas) is present is kept on the liquid phase side.
[0075] However, when the refrigerator stops its operation for a
long term, the ambient temperature may rise to vaporize a part of
the liquid phase fluid so that the bubbles may occur in dew
formation preventing pipes 62, 63 and 64. When a large amount of
bubbles occur, the liquid phase fluid does not circulate through
dew formation preventing pipes 62, 63 and 64 even when the
refrigerator operates, i.e., even when circulation pump 61
operates. Therefore, the dew formation prevention cannot be
executed.
[0076] In the operation method of the refrigerator of the
embodiment, therefore, when the refrigerator starts the operation,
it enters such an operation state that a piston reciprocates at a
higher speed than a normal speed. Thus, by reciprocating the piston
faster than the normal speed, high temperature side evaporator
(warm head) 51 attains a higher temperature than the normal
operation in the heat exchange cycle. For example, in the
refrigerator having high temperature side evaporator (warm head) 51
that attains 38.degree. C. in the normal operation, the piston
operates fast to raise the temperature of high temperature side
evaporator (warm head) 51 to 50.degree. C. until circulation pump
61 starts as illustrated in FIG. 5. The temperature is gradually
lowered after circulation pump 61 started. When high temperature
side evaporator (warm head) 51 attains to 38.degree. C., the normal
operation starts.
[0077] As described above, when bubbles are present in dew
formation preventing pipes 62, 63 and 64 at the start of the
refrigerator, the refrigerator operates to set high temperature
side evaporator (warm head) 51 to the temperature higher than that
in the normal operation so that the bubbles in dew formation
preventing pipes 62, 63 and 64 are compressed by the pressure of
the gas in high temperature side natural circulation circuit 50
that is the pipe on the gas phase side. Thus, the pressure of the
gas in high temperature side natural circulation circuit 50
increases the pressure of the fluid on the liquid phase side.
Thereby, the gas in the liquid phase changes into a liquid, and the
bubbles disappear. Thereafter, circulation pump 61 starts so that
it can operate successfully. The foregoing method prevents the
occurrence of the disadvantage at the start of the operation
[0078] FIG. 6 is a flowchart for illustrating the start processing
of the refrigerator of the first embodiment of the invention. In
the start operation of the embodiment, it is first determined in S1
whether the start switch of Stirling refrigerating engine 30 is
turned on or not. When the start switch of the refrigerating engine
is not turned on in S1, the start processing is not performed, and
the processing ends as it is. When the start switch of the
refrigerating engine is turned on in S1, processing in S2 is
executed.
[0079] In S2, it is determined whether the stop time of circulation
pump 61 is equal to or longer than a predetermined time or not. A
timer measures the stop time of circulation pump 61 from the point
of time when circulation pump 61 stopped. The data about this stop
time have been successively stored in a RAM (Random Access Memory)
in control device 90.
[0080] In S2, when the stop time of circulation pump 61 is shorter
than the predetermined time, the start processing is not performed,
and the processing ends as it is. More specifically, when the stop
time of circulation pump 61 is shorter than the predetermined time,
the probability that the bubbles have occurred in dew formation
preventing pipes 62, 63 and 64 is extremely low, and therefore the
start processing is not performed. However, instead of measuring
the stop time of circulation pump 61, the following structure and
manner may be employed. Flow meters measuring flow rates of the
liquid phase fluid in dew formation preventing pipes 62, 63 and 64
are arranged in dew formation preventing pipes 62, 63 and 64,
respectively. Values of the flow meters are read after a certain
time from the start of circulation pump 61, and it is determined
whether circulation pump 61 is operating or not. Thereby, the
determination whether the start processing is to be performed or
not is performed.
[0081] Then, in S3, a drive velocity V of the piston of Stirling
refrigerating engine 30 is set to an initial value. This drive
speed V of the piston is larger than that in the normal operation.
Then, in S4, the piston is driven at drive speed V higher than the
normal operation. Thereby, the piston is driven faster than the
normal operation so that high temperature side evaporator (warm
head) 51 of the refrigerator attains a higher temperature than the
normal operation.
[0082] Then, in S5, it is determined whether such a state is
attained or not that high temperature side evaporator (warm head)
51 is at a higher temperature than the normal operation and the
elapsed time of the operation in this high-temperature state is
equal to or longer than a predetermined time. When the
predetermined time has not elapsed in S5, the operation of
operating the piston faster than the normal operation is repeated
in S4. When high temperature side evaporator (warm head) 51
operates at a higher temperature than the normal operation for the
predetermined time or more in S5, the processing is then executed
in S6.
[0083] In S6, circulation pump 61 operates. Before this stage,
circulation pump 61 does not operate (except for the case where the
flow meters are employed) for the following reasons. When Stirling
refrigerating engine 30 stops for the predetermined time, there is
a high possibility that the bubbles have occurred in dew formation
preventing pipes 62, 63 and 64, and therefore there is a high
possibility that circulation pump 61 runs idle when it operates
before S6.
[0084] Then, in S7, it is determined whether the temperature of
high temperature side evaporator (warm head) 51 has lowered or not.
When the liquid phase fluid starts to circulate through dew
formation preventing pipes 62, 63 and 64, the heat of the hot
portion is transferred to dew formation preventing pipes 62, 63 and
64 so that the temperature of high temperature side evaporator
(warm head) 51 lowers. The fact that the temperature of the hot
portion has lowered means that circulation pump 61 starts to
circulate the liquid phase fluid in dew formation preventing pipes
62, 63 and 64. When the temperature of high temperature side
evaporator (warm head) 51 has not lowered the predetermined
temperature or more, the processing of stopping circulation pump 61
is executed in S8. The fact that the temperature of high
temperature side evaporator (warm head) 51 has not lowered means
that the liquid phase fluid in dew formation preventing pipes 62,
63 and 64 has not yet circulated. In the structure having the flow
meters measuring the flow rates of the liquid phase fluid, the
determination whether the liquid phase fluid has circulated or not
may be performed in S7 based on the flow rates of the liquid phase
fluid.
[0085] Then, in S9, the value of V is set to ((initial
value).times.1.2). Thereby, the piston operates in S4 at a further
high drive speed that is 1.2 times larger than last drive speed V
of the piston. The steps S4-S7 are repeated. When the temperature
of high temperature side evaporator (warm head) 51 has lowered a
predetermined value in S7, it is determined that the liquid phase
fluid in dew formation preventing pipes 62, 63 and 64 started the
circulation, and Stirling refrigerating engine 30 starts the normal
operation in S10. Thereafter, the start processing ends.
[0086] In the foregoing embodiment, the control is performed to
achieve the piston speed (frequency) larger than that in the normal
operation for setting high temperature side evaporator (warm head)
51 to a higher temperature than the normal operation. However,
control may be performed to achieve such a state immediately after
the start of Stirling refrigerating engine 30 that the piston speed
(frequency) is equal to that in the normal operation but a piston
stroke is larger than that in the normal operation. This control
can likewise set high temperature side evaporator (warm head) 51 to
the higher temperature than the normal operation. Therefore, even
when the control is executed to achieve the larger piston stroke
than the normal operation immediately after the start of Stirling
refrigerating engine 30, circulation pump 61 can be driven after
eliminating the bubbles in dew formation preventing pipes 62, 63
and 64.
[0087] In this specification, the time of the normal operation
means the timing of performing the operation after the start of
Stirling refrigerating engine 30 while stopping circulation pump 61
or suppressing the output of circulation pump 61.
Second Embodiment
[0088] A refrigerator of a second embodiment will now be described.
The refrigerator of the second embodiment has substantially the
same structure as that of the first embodiment already described.
Therefore, the second embodiment will be described only in
connection with portions different from those in the first
embodiment.
[0089] In the refrigerator of the first embodiment, the additional
and independent heating device is not employed, and the operation
method of the refrigerating machine, i.e., freezing machine is
changed to apply the pressure to the gas phase fluid flowing in
high temperature side natural circulation circuit 50. Instead of
these structure and method, the second embodiment employ heating
means (e.g., heater) 100 that can apply heat to the gas phase fluid
flowing through high temperature side natural circulation circuit
50, as specifically illustrated in FIG. 7. By operating this
heating means 100, it is possible to heat and thereby pressurize
the gas phase fluid flowing in high temperature side natural
circulation circuit 50. Thereby, it is possible to eliminate the
bubbles in the liquid phase fluid remaining in high temperature
side forced circulation circuit 60.
[0090] Instead of heating means 100 shown in FIG. 7, the
refrigerator may employ pressurizing means such as a pump that can
apply a pressure to the gas phase. This manner can likewise
eliminate the bubbles in the liquid phase fluid remaining in high
temperature side forced circulation circuit 60. Consequently, the
effect similar to that already described can be achieved.
[0091] The refrigerator of the second embodiment is substantially
the same as that of the first embodiment. However, as shown in FIG.
7, the refrigerator of this embodiment differs from that of the
first embodiment in that heating means 100 that can heat the gas
phase fluid flowing in high temperature side natural circulation
circuit 50 is arranged in the pipe passing the fluid from high
temperature side condenser 52 of high temperature side natural
circulation circuit 50 to high temperature side evaporator 51.
Further, control device 90 is configured to heat the gas phase
fluid by heating means 100 based on the information sent from
temperature sensor 55 that indicates the temperature of high
temperature side evaporator (warm head) 51.
[0092] Start processing of the refrigerator of the second
embodiment will now be described.
[0093] In the start processing of the refrigerator of this
embodiment, as illustrated in FIG. 8, it is first determined in S11
whether the start switch of the refrigerating machine is on or not.
When the start switch of the refrigerating machine is not on in
S11, the start processing ends. When the start switch of the
refrigerating machine is on in S11, it is determined in S12 whether
the stop time of the circulation pump is equal to or longer than a
predetermined time or not.
[0094] In S12, when the stop time of the circulation pump is
shorter than the predetermined time, the start processing ends. In
S12, when the stop time of the circulation pump is equal to or
longer than the predetermined time, the processing is executed in
S13. The steps in S11 and S12 are substantially the same as those
in S1 and S2 of the start processing in the first embodiment.
[0095] Then, in S13, the temperature to be compared with the
temperature of high temperature side evaporator (warm head) 51 is
set to the reference value of T. In S14, processing for heating by
heating means 100 is performed. Then, in S15, it is determined
whether such a situation is satisfied or not that the temperature
of high temperature side evaporator (warm head) 51 is equal to or
higher than foregoing reference value T and a duration of reference
value T is equal or longer than a predetermined time, e.g., of 5
minutes.
[0096] When it is determined in S15 that the temperature of high
temperature side evaporator (warm head) 51 equal to or higher than
reference value T has not been kept for the predetermined time or
more, the processing in step S14 continues. When it is determined
in S15 that the temperature of high temperature side evaporator
(warm head) 51 equal to or higher than reference value T has been
kept for the predetermined time or more, the processing in step S16
is executed. In S16, circulation pump 61 operates to execute the
processing. In S17, it is determined whether the temperature of
high temperature side evaporator (warm head) 51 lowers below
reference value T or not. The processing in S17 is completely the
same as that in S7 of the first embodiment.
[0097] When it is determined in S17 whether the temperature of high
temperature side evaporator (warm head) 51 has not lowered below
reference value T, processing is performed in S18 to stop
circulation pump 61. In S19, reference value T of high temperature
side evaporator (warm head) 51 is set to a new reference value
(T+5) raised, e.g., by 5 degrees. In next step S14, the temperature
higher by 5 degrees than that in the last determining processing is
handled as the reference value, and it is determined whether the
temperature of high temperature side evaporator (warm head) 51 is
higher than the reference value or not. In this manner, steps
S14-S17 are repeated.
[0098] When circulation pump 61 operates and the temperature of
high temperature side evaporator (warm head) 51 has lowered below
the predetermined temperature in S17, it is determined that the
bubbles in dew formation preventing pipes 62, 63 and 64 disappear
and the liquid phase fluid starts to flow in dew formation
preventing pipes 62, 63 and 64. Thereby, processing is performed in
S20 to stop the heating by heating means 100 (heater). Thereafter,
the normal operation starts in S21.
[0099] The foregoing embodiment employs such a manner that heating
means 100 for heating the gas phase fluid flowing through high
temperature side natural circulation circuit 50 eliminates the
bubbles in the liquid phase fluid flowing in high temperature side
forced circulation circuit 60. However, such a manner may be
employed that a pump is arranged for forcedly pressuring the gas
phase fluid flowing in high temperature side natural circulation
circuit 50, and the pressurized gas phase fluid eliminates the
bubbles in the liquid phase fluid flowing in high temperature side
forced circulation circuit 60. In this case, it is desired that the
refrigerator has pressure measuring means (e.g., pressure sensor)
that senses the pressure of the gas phase fluid flowing through
high temperature side natural circulation circuit 50, and control
device 90 receives the measured value obtained by the pressure
measuring means, and controls the pressurizing means (e.g., pump)
based on the received signal.
Third Embodiment
[0100] A third embodiment of the invention will now be described.
The refrigerator of this embodiment has substantially the same
structure as the refrigerators of the first and second embodiments.
Therefore, the following description will be given on only the
portion of this embodiment different from the first and second
embodiments.
[0101] The start processing performed by control device 90 of
Stirling refrigerating engine 30 of the third embodiment will be
described with reference to a flowchart of FIG. 9.
[0102] In the start processing, it is first determined in S21
whether a switch of the freezing machine, i.e., Stirling
refrigerating engine 30 is on or not. When the start switch of the
refrigerating machine is not on in S21, processing in S33 is
executed. When the start switch of Stirling refrigerating engine 30
is on in S21, processing in S22 is executed. In S22, Stirling
refrigerating engine 30 starts the operation. Then, in S23, the
output of circulation pump 61 is set to 0 or P.sub.1. Thereafter, a
rotation speed of radiator fan 110 is set to 0 or V.sub.1.
[0103] In S25, a timer starts. Then, in S26, it is determined
whether the foregoing timer determines the elapsing of a
predetermined time or not. When the timer does not determine the
elapsing of the predetermined time, it continues the time
measurement. When the timer determines the elapsing of the
predetermined time in S26, it is reset in S27, and processing in
S28 is executed.
[0104] In S28, a value of T1 of wall surface temperature sensor 82
is obtained. Then, a value T2 of wall surface temperature sensor 82
is obtained again in S29. Thereafter, a difference between values
T.sub.2 and T.sub.1 of the wall surface temperature sensor is
calculated in S30. Then, the difference (T.sub.2-T.sub.1) is
compared with a predetermined value K in S30. When the difference
(T.sub.2-T.sub.1) is smaller than predetermined value K in S30, the
processing in S29 and S30 is repeated. When the difference
(T.sub.2-T.sub.1) is equal to or larger than predetermined value K
in S30, the processing in S31 is repeated.
[0105] In S31, processing is performed to start circulation pump 61
or to increase the output of circulation pump 61 further from
P.sub.1. Then, in S32, control device 90 further increases the
rotation speed of radiator fan 110 further from V.sub.1.
[0106] Thereafter, a value H of wall surface humidity sensor 81 is
obtained. Then, in S34, it is determined whether value H of wall
surface humidity sensor 81 is equal to or larger than 90% or not.
When it is determined in S34 that value H of wall surface humidity
sensor 81 is equal to or larger than 90%, processing in S35 is
executed. However, when it is determined in S34 that value H of
wall surface humidity sensor 81 is smaller than 95%, the processing
in S35 is not performed, and processing in S36 is performed. In
S35, control device 90 lowers the output of circulation pump 61, or
stops circulation pump 61. In S36, the control starts to perform
the normal operation by Stirling refrigerating engine 30.
[0107] According to the start processing of the Stirling
refrigerating engine of this embodiment, the processing in S25-S27
is performed to determine whether the predetermined time has
elapsed after the turn-on of the start switch of Stirling
refrigerating engine 30. When the predetermined time has elapsed
after the start of Stirling refrigerating engine 30, the processing
is performed in S31 to start circulation pump 61 or to increase the
output of circulation pump 61. Therefore, when circulation pump 61
is not operating, the temperature of high temperature side
evaporator (warm head) 51 rises so that the temperature of the
liquid phase fluid (refrigerant: water) in dew formation preventing
pipes 62, 63 and 64 rises immediately after the start of operation
of Stirling refrigerating engine 30. Thereby, the temperature of
the liquid phase fluid (refrigerant: water) in dew formation
preventing pipe 62 rises to increase the pressure of the liquid
phase fluid. Consequently, the bubbles remaining in the liquid
phase fluid are compressed to disappear. Control device 90 has
stored the values of foregoing predetermined time and the foregoing
output of circulation pump 61 which were obtained in obtained by
experiments.
[0108] In S28-S30, a comparison is made between the initial value
of the detected temperature of wall surface temperature sensor 82
and the value of the temperature of wall surface temperature sensor
82 detected after elapsing of the predetermined time, and it is
determined that the value of the detected temperature of wall
surface temperature sensor 82 has lowered the predetermined
temperature from the initial temperature. After this determination
or confirmation, the processing is performed in S31 to start
circulation pump 61 or to increase the output of circulation pump
61. Therefore, after the temperature of the liquid phase fluid
(refrigerant: water) in dew formation preventing pipe 62 measured
by wall surface temperature sensor 82 lowered the predetermined
temperature after the start of Stirling refrigerating engine 30,
the operation of circulation pump 61 starts, or the output of
circulation pump 61 increases. Thus, the cooling space is cooled to
cause lowering of the temperature of the wall surface, and thereby
the liquid phase fluid (refrigerant: water) in dew formation
preventing pipe 62 lowers so that condensation occurs to eliminate
the bubbles remaining in dew formation preventing pipe 62.
Thereafter, the processing is performed to start circulation pump
61, or to increase the output of circulation pump 61. Consequently,
it is possible to suppress noises that occur when the bubbles in
dew formation preventing pipes 62, 63 and 64 are rapidly compressed
due to the rapid start of rotation of circulation pump 61. Control
device 90 has stored the values of foregoing predetermined
temperature K and the foregoing output of circulation pump 61 which
were obtained by experiments.
[0109] In the foregoing example, the processing in S25-S27 and the
processing in S28-S30 are both performed. However, even in a
refrigerator performing only the processing in S25-S27 or the
processing in S28-S30, it is possible to suppress noises that occur
when the bubbles in dew formation preventing pipe 62 disappear due
to the rapid operation of circulation pump 61.
[0110] After the processing in S25-S30 ends, the rotation speed of
radiator fan 110 increases in S32. Thus, rotation speed V.sub.1 of
radiator fan 110 increases only in such a state that the bubbles
remaining in dew formation preventing pipes 62, 63 and 64 have
probably disappeared. Conversely, immediately after the start of
Stirling refrigerating engine 30, the rotation speed of radiator
fan 110 is smaller than that attained after the start of
circulation pump 61. In this state, the heat exchange performance
of high temperature side condenser 52 is low. Therefore,
immediately after start of Stirling refrigerating engine 30, the
temperature of the liquid phase fluid (refrigerant: water)
remaining in dew formation preventing pipe 62 is higher than that
attained after the start of circulation pump 61. Consequently, the
pressure is applied to the liquid phase fluid in circulation pipe
61 to eliminate the bubbles. As described above, the rotation speed
of radiator fan 110 that is attained immediately after the start of
Stirling refrigerating engine 30 is controlled to be smaller than
that attained immediately after the start of circulation pump 61,
and this control can likewise suppress the noises that occur due to
the disappearance of bubbles remaining in dew formation preventing
pipe 62. Control device 90 has stored the value of rotation speed
V.sub.1 of radiator fan 110 that was obtained in advance by
experiments under the predetermined conditions.
[0111] In S33-S35, the determination about the lowering of output
of circulation pump 61 or the stop of circulation pump 61 is
performed depending on whether wall surface humidity sensor 81
exhibits the predetermined value or not. Thus, the large output of
circulation pump 61 prevents the temperature of the liquid phase
fluid in dew formation preventing pipes 62, 63 and 64 from lowering
below the ambient atmosphere temperature. Consequently, such a
situation is prevented that the temperature of the atmosphere near
dew formation preventing pipes 62, 63 and 64 as well as the
neighboring wall becomes excessively low to increase the humidity
of the atmosphere to 100% or more. Thus, the dew formation on the
wall surface of the refrigerator is prevented.
[0112] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
* * * * *