U.S. patent application number 11/723060 was filed with the patent office on 2007-09-20 for refrigerator.
This patent application is currently assigned to SANYO ELECTRIC CO., LTD.. Invention is credited to Hiroyuki Itsuki.
Application Number | 20070214824 11/723060 |
Document ID | / |
Family ID | 38222117 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070214824 |
Kind Code |
A1 |
Itsuki; Hiroyuki |
September 20, 2007 |
Refrigerator
Abstract
There is disclosed a refrigerator in which a refrigerant circuit
on a high-pressure side is operated in a supercritical state, and
an object of the refrigerator is to improve a freezing capacity
while securely preventing dew condensation at an opening edge by a
condenser. In the refrigerator including the refrigerant circuit
constituted of a compressor, the condenser, a throttle means and an
evaporator; and a dew condensation preventive pipe constituting a
part of the condenser and disposed along the opening edge of an
insulation box member, the refrigerant circuit on the high-pressure
side is operated in the supercritical state, and the dew
condensation preventive pipe is positioned on an upstream side of a
refrigerant downstream region of the condenser.
Inventors: |
Itsuki; Hiroyuki; (Ora-gun,
JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Assignee: |
SANYO ELECTRIC CO., LTD.
|
Family ID: |
38222117 |
Appl. No.: |
11/723060 |
Filed: |
March 16, 2007 |
Current U.S.
Class: |
62/279 |
Current CPC
Class: |
F25D 21/04 20130101;
F25D 2700/14 20130101; F25B 2700/21163 20130101; F25B 2400/04
20130101; F25B 6/04 20130101; F25B 9/008 20130101; F25B 40/00
20130101; F25D 2700/123 20130101; F25B 2600/2501 20130101; F25B
2309/061 20130101; F25B 2400/052 20130101 |
Class at
Publication: |
62/279 |
International
Class: |
F25B 47/00 20060101
F25B047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2006 |
JP |
2006-74476 |
Claims
1. A refrigerator comprising: a refrigerant circuit constituted of
a compressor, a condenser, a throttle means and an evaporator and
operated on a high-pressure side in a supercritical state; and a
dew condensation preventive pipe constituting a part of the
condenser and disposed along an opening edge of an insulation box
member, the condenser including at least a first condenser and a
second condenser, the dew condensation preventive pipe being
positioned between the first condenser and the second
condenser.
2. The refrigerator according to claim 1, further comprising: a
bypass pipe connected in parallel with the dew condensation
preventive pipe; and a channel control unit which controls whether
to pass a refrigerant through the dew condensation preventive pipe
or the bypass pipe.
3. The refrigerator according to claim 1 or 2, wherein carbon
dioxide is used as the refrigerant of the refrigerant circuit.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a refrigerator in which a
dew condensation preventive pipe constituting a part of a condenser
(or gas cooler or condensing heat exchanger or gas cooling heat
exchanger) of a refrigerant circuit is disposed along an opening
edge of an insulation box member in order to prevent dew
condensation of a main body. The present invention more
particularly relates to a refrigerator in which a refrigerant
circuit on a high-pressure side is operated in a supercritical
state.
[0002] Heretofore, in this type of refrigerator, an insulation box
member is constituted of a metallic outer box, an inner box made of
a hard synthetic resin and an insulation material foamed and filled
between both the boxes. In the inner box, a freezing chamber and a
refrigerating chamber are constituted so as to freeze or
refrigerate and store food and the like in the inner box. An
insulation door is disposed on a front surface of this insulation
box member, and the freezing and refrigerating chambers are
openably closed by the insulation door. Moreover, a mechanical
chamber in which a compressor and the like are to be installed is
constituted in a lower part of the insulation box member.
[0003] Furthermore, when the compressor is operated, a refrigerant
is sucked into the compressor and compressed to constitute a
high-temperature high-pressure gas, and the gas enters a condenser.
While the refrigerant flows through the condenser, heat exchange
between the refrigerant and ambient air is performed. The
refrigerant rejects (or transfers) heat and is condensed. After a
pressure of the refrigerant which has condensed in the condenser is
reduced by a throttle means, the refrigerant enters an evaporator
and evaporates. At this time, the refrigerant absorbs the heat from
a surrounding to exhibit a cooling function. The air subjected to
the heat exchange between the air and the refrigerant and cooled in
the evaporator is circulated through chambers such as the freezing
chamber and the refrigerating chamber by blowing means such as a
fan to cool objects stored in the chambers.
[0004] In such a refrigerator, when the heat leaks from a portion
between the insulation box member and the insulation door, a
surface temperature in the vicinity of this portion drops below a
temperature (outside air temperature) around a position where the
refrigerator is installed, and the temperature is not more than a
dew point. In this case, a disadvantage occurs that a moisture in
the air is attached, that is, so-called dew condensation is
generated. Therefore, a heater is installed in a portion of the
refrigerator in which the dew condensation is easily generated to
thereby heat the portion. In consequence, the generation of the dew
condensation in such a portion has been prevented.
[0005] However, a disadvantage occurs that a cooling performance
deteriorates or power consumption increases owing to the heat of
the heater. To solve such a problem, a refrigerant downstream
region of the condenser of the refrigerant circuit is disposed in
the portion in which the dew condensation is easily generated. The
portion is thus heated to thereby prevent the generation of the dew
condensation. Specifically, for example, a pipe constituting the
refrigerant downstream region of the condenser of the refrigerator
is disposed along an opening edge of the insulation box member,
that is, the refrigerant pipe of the refrigerant downstream region
of the condenser is used as the dew condensation preventive pipe.
In consequence, a high-temperature high-pressure refrigerant gas
compressed by the compressor is allowed to condense in the
condenser. The refrigerant condenses at a constant temperature (a
predetermined condensation temperature without any temperature
change). Therefore, the opening edge can be heated by the heat of
the refrigerant passed through the condenser (including a dew
condensation preventive pipe) to prevent such dew condensation
(see, e.g., Japanese Patent Application Laid-Open Nos. 7-239178,
10-197122).
[0006] In addition, in recent years, such a refrigerator cannot use
a heretofore used chlorofluorocarbon-based refrigerant owing to a
problem of global environment destruction. Therefore, an attempt to
use carbon dioxide (CO.sub.2) which is a natural refrigerant as a
substitute for the chlorofluorocarbon-based refrigerant.
[0007] When the carbon dioxide refrigerant is compressed, the
refrigerant circuit on the high-pressure side is sometimes brought
into a supercritical state. When the refrigerant circuit on the
high-pressure side is brought into the supercritical state in this
manner, the refrigerant does not condense in the condenser, and
rejects the heat while maintaining the supercritical state.
Therefore, the temperature of the refrigerant drops owing to the
hat rejection. To solve this problem, a refrigerant temperature at
an outlet of the dew condensation preventive pipe in the
refrigerant downstream region of the condenser needs to be
maintained at a value sufficient for preventing the dew
condensation along the opening edge. That is, the refrigerant
temperature at an outlet of the condenser has to be maintained at a
temperature which is not less than the dew point so that the dew
condensation is not generated. Therefore, the refrigerant
temperature at the outlet of the condenser cannot be lowered to a
value sufficient for securing a freezing capability, and specific
enthalpy of the refrigerant flowing through the evaporator also
increases. In consequence, a problem has occurred that the freezing
capability of the evaporator remarkably deteriorates, and the
cooling in the freezing chamber and the refrigerating chamber is
obstructed.
SUMMARY OF THE INVENTION
[0008] The present invention has been developed to solve the
problem of such a conventional technology, and an object is to
improve a freezing capability while securely preventing dew
condensation along an opening edge by a condenser in a refrigerator
in which a refrigerant circuit on a high-pressure side is operated
in a supercritical state.
[0009] This is, a refrigerator of a first invention comprises: a
refrigerant circuit constituted of a compressor, a condenser, a
throttle means and an evaporator and operated on a high-pressure
side in a supercritical state; and a dew condensation preventive
pipe constituting a part of the condenser and disposed along an
opening edge of an insulation box member. The refrigerator is
characterized in that the condenser includes at least a first
condenser and a second condenser and that the dew condensation
preventive pipe is positioned between the first condenser and the
second condenser.
[0010] A second invention is characterized in that the above
invention further comprises: a bypass pipe connected in parallel
with the dew condensation preventive pipe; and a channel control
unit which controls whether to pass a refrigerant through the dew
condensation preventive pipe or the bypass pipe.
[0011] According to a third invention, the above inventions are
characterized in that carbon dioxide is used as the refrigerant of
the refrigerant circuit.
[0012] According to the first invention, in the refrigerator
comprising: the refrigerant circuit constituted of the compressor,
the condenser, the throttle means and the evaporator and operated
on the high-pressure side in the supercritical state; and the dew
condensation preventive pipe constituting a part of the condenser
and disposed along the opening edge of the insulation box member,
the condenser includes at least the first condenser and the second
condenser, and the dew condensation preventive pipe is positioned
between the first condenser and the second condenser. Therefore,
while a temperature at an outlet of the dew condensation preventive
pipe is set to a value sufficient for preventing dew condensation
along the opening edge, a temperature of the refrigerant in a
refrigerant downstream region can sufficiently be lowered.
[0013] In consequence, a refrigerant temperature at an outlet of
the condenser can be lowered to a value sufficient for securing a
freezing capacity. While the dew condensation along the opening
edge is prevented, the freezing capacity can be improved.
[0014] Moreover, in the present invention, since the dew
condensation preventive pipe is disposed between the first
condenser and the second condenser, a temperature of the dew
condensation preventive pipe sometimes rises more than necessary
during pull-down or the like. However, in a case where the
refrigerator further comprises: the bypass pipe connected in
parallel with the dew condensation preventive pipe; and the channel
control unit which controls whether to pass the refrigerant through
the dew condensation preventive pipe or the bypass pipe as in the
second invention, when the temperature of the dew condensation
preventive pipe rises more than necessary, the refrigerant can be
passed through the bypass pipe to prevent an excessive temperature
rise of the dew condensation preventive pipe.
[0015] In consequence, a disadvantage can be avoided in advance
that owing to the excessive temperature rise of the dew
condensation preventive pipe, a feeling of discomfort is given to a
user or the user gets burnt when touching the pipe. Moreover,
safety can be secured.
[0016] Especially, according to the present invention, carbon
dioxide can be used as the refrigerant of the refrigerator as in
the third invention. This also contributes to solution of an
environmental problem.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a refrigerant circuit diagram of a refrigerator
according to one embodiment of the present invention;
[0018] FIG. 2 is a schematic diagram schematically showing a
refrigerant circuit of the refrigerator of FIG. 1;
[0019] FIG. 3 is the Mollier diagram of the refrigerator of the
present embodiment;
[0020] FIG. 4 is a refrigerant circuit diagram of a refrigerator
according to another embodiment of the present invention;
[0021] FIG. 5 is the Mollier diagram of the refrigerator of FIG.
5;
[0022] FIG. 6 is a refrigerant circuit diagram of a refrigerator
according to still another embodiment of the present invention;
[0023] FIG. 7 is a refrigerant circuit diagram of a conventional
refrigerator;
[0024] FIG. 8 is a schematic diagram schematically showing a
refrigerant circuit of the refrigerator of FIG. 7;
[0025] FIG. 9 is the Mollier diagram of the refrigerator of FIG. 7
in a case where a conventional refrigerant is used (in a case where
a supercritical pressure is not achieved in a refrigerant circuit
on a high-pressure side); and
[0026] FIG. 10 is the Mollier diagram of the refrigerator of FIG. 7
in a case where a refrigerant circuit on a high-pressure side is
operated in a supercritical state.
DESCRIPTION OF THE PREFERABLE EMBODIMENTS
[0027] The present invention is directed to a refrigerator in which
a refrigerant circuit on a high-pressure side is operated in a
supercritical state and in which a dew condensation preventive pipe
constituting a part of a condenser is disposed along an opening
edge of an insulation box member to prevent dew condensation along
the opening edge. The present invention has been developed to
eliminate a disadvantage that specific enthalpy of a refrigerant
flowing through an evaporator increases and a freezing capacity
deteriorates in a case where a temperature of the refrigerant
flowing through the dew condensation preventive pipe is maintained
at a value sufficient for preventing dew condensation along the
opening edge. An object to improve the freezing capacity while
securely preventing dew condensation along the opening edge of the
refrigerator is realized by positioning the dew condensation
preventive pipe constituting a part of the condenser between a
first condenser and a second condenser. Embodiments of the present
invention will hereinafter be described with reference to the
drawings.
Embodiment 1
[0028] FIG. 1 shows a refrigerant circuit diagram of a refrigerator
according to one embodiment of the present invention, and FIG. 2
shows a schematic diagram of a dew condensation preventive pipe
disposed along an opening edge of an insulation box member of the
refrigerator, respectively. A main body of a refrigerator 1 of the
embodiment is constituted of an outer box 2 having a front opening
and formed of a steel plate; an inner box 3 made of a thin hard
synthetic resin (e.g., an ABS resin); an insulation box member 4
made of foamed polyurethane foamed and filled between both the
boxes; and an insulation door (not shown) which openably closes the
front opening of the insulation box member 4.
[0029] The inside of the insulation box member 4 is vertically
divided by a partition wall 5 into, for example, a refrigerating
chamber 6 cooled at a refrigerating temperature (e.g., about
+5.degree. C.) above the partition wall 5 and a freezing chamber 7
frozen at a freezing temperature (e.g., about -20.degree. C.) under
the partition wall 5.
[0030] An indoor temperature sensor 10 for detecting a temperature
in the refrigerating chamber 6 is disposed in the refrigerating
chamber 6, and an indoor temperature sensor 11 for detecting a
temperature in the freezing chamber 7 is disposed in the freezing
chamber 7. These indoor temperature sensors 10, 11 are connected to
a controller 50 described later, respectively.
[0031] Moreover, a door switch for detecting opening/closing of the
insulation door (not shown) is disposed on an inner portion of the
front surface of the insulation box member 4. An outside air
temperature sensor 12 (not shown in FIG. 2) for detecting an
outside air temperature around the refrigerator 1 is disposed in
the vicinity of this door switch. The outside air temperature
sensor 12 is connected to the controller 50.
[0032] Furthermore, a mechanical chamber (not shown) is constituted
in an outer lower part of the inner box 3 which is a lower part of
the insulation box member 4. The mechanical chamber contains a
compressor 21 constituting a part of a refrigerant circuit of a
cooling device of the refrigerator 1 according to the present
invention and the like.
[0033] In the cooling device of the refrigerator 1 of the present
invention, as shown in FIG. 1, the refrigerant circuit is
constituted of the compressor 21, a condenser 22, a capillary tube
23 as a throttle means and an evaporator 24. In this case, a
discharge-side pipe 40 of the compressor 21 is connected to a
refrigerant pipe 22A constituting a first condenser which is a
refrigerant upstream region of the condenser 22. A refrigerant pipe
22C constituting a second condenser which is a refrigerant
downstream region of the condenser 22 is connected to a refrigerant
pipe 42 connected to an inlet of the capillary tube 23. Moreover, a
refrigerant-inlet-side pipe 45 of the evaporator 24 is connected to
an outlet of the capillary tube 23. An outlet of the evaporator 24
is connected to a suction-side pipe 41 of the compressor 21 to
constitute the refrigerant circuit.
[0034] Moreover, a part of the suction-side pipe 41 which connects
the evaporator 24 to the compressor 21 on a suction side is
disposed so that heat exchange between the part and the capillary
tube 23 is performed. In consequence, an internal heat exchanger 25
is constituted. The internal heat exchanger 25 is formed by
arranging the capillary tube 23 and the suction-side pipe 41
connected to the outlet of the evaporator 24 so that the heat
exchange between the tube and the pipe can be performed. While the
refrigerant flows through the internal heat exchanger 25, the
refrigerant exits from the condenser 22 and enters the capillary
tube 23. The refrigerant is subjected to heat exchange between the
refrigerant and a refrigerant flowing through the suction-side pipe
41 disposed so as to perform heat exchange, the refrigerant rejects
the heat, and a pressure of the refrigerant drops. Conversely,
while the refrigerant exiting from the evaporator 24 flows through
the suction-side pipe 41 of the internal heat exchanger 25, heat
exchange between the refrigerant and the refrigerant flowing
through the capillary tube 23 is performed, and the refrigerant is
heated.
[0035] Here, the condenser 22 will be described. The condenser 22
is constituted by successively connecting the refrigerant pipe 22A
(the first condenser) extended along a side surface of the metallic
outer box 2 of the insulation box member 4 and a top surface on an
insulation material side; a dew condensation preventive pipe 22B
disposed along an opening edge 4A of the insulation box member 4;
and the refrigerant pipe 22C (the second condenser) disposed on a
bottom surface of the mechanical chamber constituted in a lowermost
part of the insulation box member 4. While the refrigerant flows
through the refrigerant pipes 22A, 22B and 22C of the condenser 22,
heat exchange between the refrigerant and a surrounding is
performed so that the refrigerant rejects the heat. Moreover, the
refrigerant pipe 22A extended along the side surface of the
metallic outer box 2 of the insulation box member 4 and the top
surface on the insulation material side constitutes the refrigerant
upstream region of the condenser 22. The dew condensation
preventive pipe 22B disposed along the opening edge 4A of the
insulation box member 4 constitutes a refrigerant midstream region
of the condenser 22. The refrigerant pipe 22C disposed on the
bottom surface of the mechanical chamber constituted in the
lowermost part of the insulation box member 4 constitutes the
refrigerant downstream region of the condenser 22. That is, the
condenser 22 of the present embodiment is divided into three flow
regions including the refrigerant upstream region, the refrigerant
midstream region and the refrigerant downstream region. The
refrigerant rejects the heat in the flow regions.
[0036] Moreover, the dew condensation preventive pipe 22B disposed
along the opening edge 4A of the insulation box member 4 is
positioned in a position on an upstream side of the refrigerant
downstream region, that is, in the refrigerant midstream region.
The dew condensation preventive pipe 22B of the present embodiment
is formed of a material such as copper or aluminum, and stored in a
groove (not shown) formed between the outer box 2 and the inner box
3. Furthermore, one end of the dew condensation preventive pipe 22B
is connected to the refrigerant pipe 22A which is the refrigerant
upstream region of the condenser 22 at a lower portion of one end
(A in FIG. 2) of the front surface of the insulation box member 4.
The other end of the pipe is connected to the refrigerant pipe 22C
which is the refrigerant downstream region of the condenser 22 at a
lower portion of the other end (B in FIG. 2) of the front surface
of the insulation box member 4.
[0037] Specifically, as shown in FIG. 2, the dew condensation
preventive pipe 22B of the refrigerator 1 of the present embodiment
rises upwards from a right lower end of the insulation box member 4
to a predetermined height, then bends at 90.degree. in a left
direction, extends in a horizontal direction to reach a left end,
turns from the left end in a U-shape, and extends to the right side
along a pipe extended from the right end to the left end. Moreover,
the dew condensation preventive pipe rises upwards from the right
end to a predetermined height, bends at 90.degree. in the left
direction, extends in the horizontal direction, turns from the left
end in the U-shape, and extends along a pipe extended from the
right end to the left end to extend toward the right side.
Furthermore, the dew condensation preventive pipe rises upwards
from the right end, extends to an upper end, and bends at
90.degree. from the upper end toward the left side to extend in the
left direction. In addition, the pipe lowers from a left upper end
to a lower end in a vertical direction. The pipe is extended in the
groove (not shown) of the opening edge 4A in this manner.
[0038] The controller 50 is control means for controlling the
refrigerator of the present embodiment, and is constituted of a
general-purpose microcomputer. Moreover, the controller 50 on an
input side is connected to the indoor temperature sensors 10, 11,
the outside air temperature sensor 12 and the like. The controller
on an outlet side is connected to the compressor 21 and a fan 24F
of the evaporator 24.
[0039] Moreover, the controller 50 controls an operation of the
compressor 21 and the number of rotations of the fan 24F of the
evaporator 24 based on the temperatures in the freezing chamber and
the refrigerating chamber detected by the indoor temperature
sensors 10, 11.
[0040] It is to be noted that carbon dioxide which is a natural
refrigerant is used as the refrigerant of the refrigerator 1 of the
present embodiment, and the refrigerant circuit 20 on a
high-pressure side is operated in a supercritical state.
[0041] Next, an operation of the refrigerator 1 of the present
invention constituted as described above will be described with
reference to the Mollier diagram of FIG. 3. The controller 50
basically operates the compressor 21 based on outputs of the indoor
temperature sensors 10, 11. Especially, the controller performs
ON-OFF control of the compressor 21 based on the temperature in the
freezing chamber 7 detected by the indoor temperature sensor 11. In
consequence, the operation is performed so that the temperatures in
the chambers are in a range of an upper limit temperature set above
a target temperature to a lower limit temperature set below the
target temperature.
[0042] Moreover, if the temperature in the freezing chamber 7 rises
in excess of the upper limit temperature of the target temperature
(the target temperature is, e.g., -20.degree. C.), the controller
50 drives the compressor 21 to start a compressing operation. In
consequence, a low-temperature low-pressure carbon dioxide
refrigerant is sucked into the compressor 21 (a state A of FIG. 3),
compressed by the compressor 21 to constitute a high-temperature
high-pressure refrigerant gas, and discharged from the compressor
21 to the refrigerant pipe 40. At this time, the carbon dioxide
refrigerant is compressed and brought into the supercritical state
(a state B of FIG. 3).
[0043] The refrigerant entering the refrigerant pipe 40 and having
the supercritical state enters the refrigerant pipe 22A extended
along the side surface of the metallic outer box 2 of the
insulation box member 4 and the top surface on the insulation
material side and constituting the refrigerant upstream region of
the condenser 22. While the refrigerant flows through the
refrigerant pipe 22A, the refrigerant rejects the heat. At this
time, in the refrigerant pipe 22A, the refrigerant rejects the heat
while maintaining the supercritical state. In consequence, enthalpy
of the refrigerant drops as much as .DELTA.H1. That is, in the
refrigerant pipe 22A, the only temperature of the refrigerant drops
without any state change. The refrigerant is brought into a state C
of FIG. 3.
[0044] Moreover, the refrigerant which has rejected the heat in the
refrigerant pipe 22A then passes through the dew condensation
preventive pipe 22B which is disposed along the opening edge 4A of
the insulation box member 4 and which is the refrigerant midstream
region of the condenser 22. In this process, the refrigerant
rejects the heat while maintaining the supercritical state. In
consequence, the enthalpy of the refrigerant drops as much as
.DELTA.H2. Therefore, in the dew condensation preventive pipe 22B,
the only temperature of the refrigerant drops without any state
change, and the refrigerant is brought into a state D of FIG.
3.
[0045] The refrigerant which has rejected the heat in the dew
condensation preventive pipe 22B then passes through the
refrigerant pipe 22C which is disposed on the bottom surface of the
mechanical chamber constituted in the lowermost part of the
insulation box member 4 and which is the refrigerant downstream
region of the condenser 22, and the refrigerant rejects the heat.
At this time, the refrigerant still maintains the supercritical
state. The enthalpy further drops as much as .DELTA.H3 owing to the
heat rejection in the refrigerant pipe 22C. Therefore, in the
refrigerant pipe 22C, the only temperature of the refrigerant drops
without any state change, and the refrigerant is brought into a
state E of FIG. 3.
[0046] Subsequently, the refrigerant exiting from the condenser 22
enters the capillary tube 23, and the heat exchange between the
refrigerant and a refrigerant flowing through the suction-side pipe
41 is performed, the pipe being disposed so as to perform the heat
exchange between the pipe and the capillary tube 23. The
refrigerant is thus further cooled (the enthalpy of the refrigerant
further drops as much as .DELTA.H4). Moreover, the refrigerant
expands owing to the pressure drop in the capillary tube 23, is
brought into a state F of FIG. 3, and reaches the evaporator 24.
The refrigerant at the inlet of the evaporator 24 has a two-phase
mixed state in which a liquid refrigerant and a vapor refrigerant
are mixed. Moreover, in the evaporator 24, the liquid-phase
refrigerant evaporates to constitute the vapor refrigerant. Ambient
air is cooled by a heat absorbing function of this refrigerant
during the evaporation. The cooled air is circulated through the
chambers 6, 7 by the fan 24F (a state G of FIG. 3).
[0047] Moreover, the low-temperature low-pressure refrigerant
exiting from the evaporator 24 enters the suction-side pipe 41, and
passes through the internal heat exchanger 25. In the internal heat
exchanger 25, the low-temperature low-pressure refrigerant exiting
from the evaporator 24 is subjected to the heat exchange between
this refrigerant and the refrigerant flowing through the capillary
tube 23 (the state A of FIG. 3) and heated. Subsequently, the
refrigerant exits from the internal heat exchanger 25, and is
sucked into the compressor. This cycle is repeated. When such an
operation is repeated, the chambers 6, 7 are gradually cooled.
[0048] In addition, when the refrigerant circuit on the
high-pressure side is brought into the supercritical state as
described above, the refrigerant does not condense in the condenser
22. Therefore, while the refrigerant maintains the supercritical
state, the refrigerant rejects the heat, and the only temperature
of the refrigerant drops.
[0049] Here, a conventional refrigerator will be described with
reference to FIGS. 7 and 8. It is to be noted that in FIGS. 7 and
8, components denoted with the same numerals as those of FIGS. 1
and 2 perform the same or similar functions or produce the same or
similar effects. Therefore, detailed description thereof is
omitted. In a conventional refrigerator 100, a condenser 122 is
divided into two flow regions including a refrigerant upstream
region and a refrigerant downstream region. In consideration of a
refrigerant temperature rise on a high-pressure side during
pull-down or under a high load, a dew condensation preventive pipe
122B is disposed in the refrigerant downstream region of the
condenser 122. That is, the refrigerant upstream region of the
condenser 122 is constituted by a refrigerant pipe 122A disposed
along a side surface of a metallic outer box 102, a top surface on
an insulation material side and a bottom surface of a mechanical
chamber constituted in a lowermost part, and the refrigerant
downstream region is constituted by the dew condensation preventive
pipe 122B of an insulation box member 4.
[0050] In the refrigerator 100 including the refrigerant circuit
constituted as described above, a compressor 21 is driven to
perform a compressing operation by use of a conventional
refrigerant, that is, a refrigerant (e.g., a
chlorofluorocarbon-based refrigerant or the like) which is not
brought into a supercritical state on a high-pressure side. In this
case, as shown in the Mollier diagram of FIG. 9, the refrigerant
condenses in the condenser 122. Much of the refrigerant rejects
heat in a two-phase region (a two-phase mixed state) of a gas and a
liquid. Therefore, a refrigerant temperature in the condenser 122
hardly changes, and the refrigerant temperature at an outlet of the
dew condensation preventive pipe 122B is a predetermined
condensation temperature which is not less than a dew point. In
consequence, dew condensation along an opening edge 4A can securely
be eliminated.
[0051] However, when a carbon dioxide refrigerant or the like is
used as in the present embodiment, the refrigerator on the
high-pressure side is sometimes brought into the supercritical
state. In this case, since the refrigerant does not condense in the
condenser 122, the temperature drops. In the refrigerator 100
including the conventional constitution, the refrigerant
temperature at the outlet of the dew condensation preventive pipe
122B might drop below the dew point. When the refrigerant
temperature at the outlet of the dew condensation preventive pipe
122B drops below the dew point, a moisture in air around the
refrigerator 1 is attached in the vicinity of the dew condensation
preventive pipe 122B, and the dew condensation is generated along
the opening edge 4A.
[0052] To prevent such dew condensation, the refrigerant
temperature at the outlet of the dew condensation preventive pipe
122B needs to be maintained at a value sufficient for preventing
dew condensation along the opening edge 4A, that is, a dew point or
more, specifically at a temperature which is about at least
+4.degree. C. higher than a temperature around the refrigerator 100
(e.g., in a case where the ambient temperature is +30.degree. C.,
the refrigerant temperature at the outlet of the dew condensation
preventive pipe 122B needs to be maintained at +34.degree. C. or
more). However, in the refrigerator 100 having the conventional
constitution, when the refrigerant temperature at the outlet of the
dew condensation preventive pipe 122B is set to the above
temperature or more (e.g., +34.degree. C. or more), as shown in the
Mollier diagram of FIG. 10, the refrigerant temperature at an
outlet of the condenser 122 rises, and the temperature cannot be
lowered to a value sufficient for securing a freezing capacity of
an evaporator 24. As a result, specific enthalpy of the refrigerant
flowing through the evaporator 24 rises, and an enthalpy difference
(q of FIG. 10) of the evaporator 24 cannot sufficiently be secured.
Therefore, a problem has occurred that the freezing capacity of the
evaporator 24 remarkably deteriorates, and cooling in a
refrigerating chamber 6 or a freezing chamber 7 is obstructed.
[0053] To solve such a problem, it is preferable that the dew
condensation preventive pipe 122B is disposed in a position where
the refrigerant temperature at the outlet of the dew condensation
preventive pipe 122B is not more than the dew point. However, for
example, when the dew condensation preventive pipe 122B is disposed
in the refrigerant upstream region of the condenser 122, the
high-temperature high-pressure refrigerant compressed by the
compressor 21 enter the dew condensation preventive pipe 122B as it
is. Therefore, the temperature along the opening edge 4A rises.
When performing an operation such as opening or closing of the
refrigerator 1, a user might feel uncomfortable. When toughing the
opening edge 4A, the user might get burnt. Furthermore, since the
opening edge 4A has an excessively high temperature, there is a
disadvantage that a cooling capacity of the refrigerator 100
deteriorates.
[0054] To solve the problem, in the present invention, the dew
condensation preventive pipe 22B is disposed in a position on an
upstream side of the refrigerant downstream region of the condenser
22. Specifically, as described above, it is constituted that the
condenser 22 is divided into three flow regions including the
refrigerant upstream region, the refrigerant midstream region and
the refrigerant downstream region and that the dew condensation
preventive pipe 22B is disposed in the refrigerant midstream region
of the condenser 22. The dew condensation preventive pipe 22B is
positioned on the upstream side of the refrigerant downstream
region of the condenser 22 in this manner. In consequence, the
temperature at the outlet of the dew condensation preventive pipe
22B can be set to a value sufficient for preventing the dew
condensation along the opening edge 4A. Furthermore, when the dew
condensation preventive pipe 22B is positioned on a downstream side
of the refrigerant upstream region of the condenser 22, it is
possible to avoid the above-described disadvantage that the
refrigerant temperature at the inlet of the dew
condensation-preventive pipe 22B excessively rises. Furthermore, in
a case where the refrigerant pipe 22C constituting the refrigerant
downstream region of the condenser 22 is disposed at the outlet of
the dew condensation preventive pipe 22B, even if the temperature
of the refrigerant cannot sufficiently be lowered in the dew
condensation preventive pipe 22B, the refrigerant is further
allowed to reject the heat. The temperature is sufficiently
lowered, and the refrigerant temperature at the outlet of the
condenser 22 can be lowered to a value sufficient for securing the
freezing capacity of the evaporator 24.
[0055] That is, as compared with a case where the conventional
refrigerator 100 is used as shown in FIG. 3, the enthalpy
difference in the evaporator 24 can be enlarged. That is, the
enthalpy difference of the evaporator 24 is q' larger than that in
the conventional refrigerator 100 shown in FIG. 10, and the
freezing capacity of the evaporator 24 can be improved.
[0056] As described above in detail, while securely preventing the
dew condensation along the opening edge 4A in the refrigerator 1 of
the present invention, the freezing capacity of the evaporator 24
can be improved.
Embodiment 2
[0057] It is to be noted that it has been described in Embodiment 1
that the capillary tube 23 is used as a throttle means. However, as
shown in FIG. 4, an expansion valve 26 may be used as the throttle
means, and an open degree of the expansion valve 26 may be
controlled by a controller 50. In this embodiment, a refrigerant
pipe 42 before the expansion valve 26 (on an upstream side of the
expansion valve 26) and a suction-side pipe 41 exiting from an
evaporator 24 are arranged so as to perform heat exchange. In
consequence, an internal heat exchanger 27 is constituted. A
refrigerant circuit of a refrigerator of the present embodiment
shown in FIG. 4 is common to Embodiment 1 described above in many
respects. Therefore, detailed description of a constitution which
performs the same function as that of the refrigerator 1 of
Embodiment 1 and a function similar to that of the refrigerator or
which produces the same effect or a similar effect is omitted.
[0058] Next, an operation of the refrigerator 1 of the present
embodiment will be described with reference to the Mollier diagram
of FIG. 5. Since a basic control operation of the controller 50 is
common to Embodiment 1, detailed description thereof is
omitted.
[0059] Moreover, if a temperature in a freezing chamber 7 rises in
excess of an upper limit temperature of a target temperature (e.g.,
the target temperature is -20.degree. C.), the controller 50 drives
a compressor 21 to start a compressing operation. In consequence, a
low-temperature low-pressure carbon dioxide refrigerant is sucked
into the compressor 21 (a state A of FIG. 5), compressed by the
compressor 21 to constitute a high-temperature high-pressure
refrigerant gas, and discharged from the compressor 21 to a
refrigerant pipe 40. At this time, the carbon dioxide refrigerant
is compressed and brought into a the supercritical state (a state B
of FIG. 5).
[0060] The refrigerant entering the refrigerant pipe 40 and having
the supercritical state enters a refrigerant pipe 22A extended
along a side surface of a metallic outer box 2 of an insulation box
member 4 and a top surface on an insulation material side and
constituting a refrigerant upstream region of a condenser 22. While
the refrigerant flows through the refrigerant pipe 22A, the
refrigerant rejects heat. At this time, in the refrigerant pipe
22A, the refrigerant rejects the heat while maintaining the
supercritical state. In consequence, enthalpy of the refrigerant
drops as much as .DELTA.H1. Therefore, in the refrigerant pipe 22A,
the only temperature of the refrigerant drops without any state
change. The refrigerant is brought into a state C of FIG. 5).
[0061] Moreover, the refrigerant which has rejected the heat in the
refrigerant pipe 22A then passes through a dew condensation
preventive pipe 22B which is disposed along an opening edge 4A of
the insulation box member 4 and which is a refrigerant midstream
region of the condenser 22. In this process, the refrigerant
rejects the heat while maintaining the supercritical state. In
consequence, the enthalpy of the refrigerant drops as much as
.DELTA.H2. Therefore, in the dew condensation preventive pipe 22B,
the only temperature of the refrigerant drops without any state
change, and the refrigerant is brought into a state D of FIG.
5.
[0062] The refrigerant which has rejected the heat in the dew
condensation preventive pipe 22B then passes through a refrigerant
pipe 22C which is disposed on a bottom surface of a mechanical
chamber constituted in a lowermost part of the insulation box
member 4 and which is a refrigerant downstream region of the
condenser 22. Furthermore, the refrigerant rejects the heat. At
this time, the refrigerant still maintains the supercritical state.
Since the refrigerant rejects the heat in the refrigerant pipe 22C,
the enthalpy of the refrigerant further drops as much as .DELTA.H3.
Therefore, in the refrigerant pipe 22C, the refrigerant further
rejects the heat in this process without any state change, the
temperature drops, and the refrigerant is brought into a state EI
of FIG. 5.
[0063] Moreover, the refrigerant exiting from the condenser 22
enters the refrigerant pipe 42, and passing through the internal
heat exchanger 27. While the refrigerant passes through the
internal heat exchanger 27, the heat exchange between the
refrigerant exiting from the condenser 22 and a refrigerant flowing
through a suction-side pipe 41 is performed to further cool the
refrigerant (the enthalpy of the refrigerant further drops as much
as .DELTA.H4). The refrigerant is brought into a state EII of FIG.
5.
[0064] Subsequently, the refrigerant exiting from the internal heat
exchanger 27 expands owing to the pressure drop in the expansion
valve 26, is brought into a state F of FIG. 5, and reaches the
evaporator 24. Here, the refrigerant has a two-phase mixed state in
which a liquid refrigerant and a vapor refrigerant are mixed.
Moreover, in the evaporator 24, the liquid-phase refrigerant
evaporates to constitute the vapor refrigerant. Ambient air is
cooled by a heat absorbing function of this refrigerant during the
evaporation. The cooled air is circulated through the chambers 6, 7
by a fan (a state G of FIG. 5).
[0065] Moreover, the low-temperature low-pressure refrigerant
exiting from the evaporator 24 enters the suction-side pipe 41, and
passes through the internal heat exchanger 27. In the internal heat
exchanger 27, the low-temperature low-pressure refrigerant exiting
from the evaporator 24 is subjected to the heat exchange between
this refrigerant and the refrigerant flowing through the
refrigerant pipe 42 and heated. Subsequently, the refrigerant exits
from the internal heat exchanger 27, and is sucked into the
compressor 21. This cycle is repeated. When such an operation is
repeated, the chambers 6, 7 are gradually cooled.
[0066] Even in the refrigerator of the present embodiment described
above in detail, the dew condensation preventive pipe 22B is
disposed in the refrigerant midstream region on the upstream side
of the refrigerant downstream region of the condenser 22 in the
same manner as in the above embodiment. In consequence, the
temperature at the outlet of the dew condensation preventive pipe
22B can be set to a value sufficient for preventing the dew
condensation along the opening edge 4A. Furthermore, it is possible
to avoid a disadvantage that the refrigerant temperature at the
inlet of the dew condensation preventive pipe 22B excessively
rises. In addition, in a case where the refrigerant pipe 22C
constituting the refrigerant downstream region of the condenser 22
is disposed at the outlet of the dew condensation preventive pipe
22B, even if the temperature of the refrigerant cannot sufficiently
be lowered in the dew condensation preventive pipe 22B, the
refrigerant is further allowed to reject the heat. The temperature
is sufficiently lowered, and the refrigerant temperature at the
outlet of the condenser 22 can be lowered to a value sufficient for
securing a freezing. capacity of the evaporator 24.
[0067] That is, as compared with a case where the conventional
refrigerator 100 is used as shown in FIG. 5, an enthalpy difference
in the evaporator 24 can be enlarged. That is, the enthalpy
difference of the evaporator is q' larger than that in the
conventional refrigerator 100 shown in FIG. 10, and the freezing
capacity of the evaporator 24 can be improved. In consequence,
while securely preventing the dew condensation along the opening
edge 4A, the freezing capacity of the evaporator 24 can be
improved.
Embodiment 3
[0068] In addition, when a dew condensation preventive pipe 22B is
moved from a refrigerant downstream region of a conventional
condenser to an upstream side as in the above embodiments, a usual
operation is not especially obstructed. However, a temperature of a
refrigerant flowing through the dew condensation preventive pipe
22B might rise more than necessary during pull-down or under a high
load. That is, if the refrigerant temperature of a refrigerant
circuit on a high-pressure side abnormally rises during the
pull-down or under the high load, during heat rejection in a
refrigerant pipe 22A which is a refrigerant upstream region of a
condenser 22, the refrigerant cannot sufficiently reject heat and
the temperature cannot be lowered. Therefore, a high-temperature
refrigerant sometimes enters the dew condensation preventive pipe
22B. Since the dew condensation-preventive pipe 22B is positioned
along an opening edge 4A of an insulation box member 4, a user
might tough the pipe when opening or closing a refrigerator 1. If
such a high-temperature refrigerant flows through the dew
condensation preventive pipe 22B, a feeling of discomfort might be
given to the user. Moreover, the user might touch the opening edge
4A to get burnt.
[0069] To solve the problem, a bypass pipe 28 is connected in
parallel with the dew condensation preventive pipe 22B so as to
extend around the dew condensation preventive pipe 22B (one end of
the bypass pipe 28, is connected to a position A shown in FIG. 6,
and the other end of the bypass pipe 28 is connected to a position
B so that the bypass pipe extends around the dew condensation
preventive pipe 22B). Moreover, a channel control unit is disposed
which controls whether to pass the refrigerant through the dew
condensation preventive pipe 22B or the bypass pipe 28. When a
temperature of the dew condensation preventive pipe 22B rises more
than necessary, the channel control unit executes control so that
the refrigerant flows through the bypass pipe 28, and prevents an
excess temperature rise of the dew condensation preventive pipe
22B. In the present embodiment, a three way valve 29 is disposed as
the channel control unit on an inlet side of the bypass pipe 28,
that is, the position A shown in FIG. 6. Moreover, a refrigerant
temperature sensor 13 for detecting the temperature of the
refrigerant flowing through the dew condensation preventive pipe
22B is disposed at an inlet of the dew condensation preventive pipe
22B or an outlet of the refrigerant pipe 22A of the condenser 22
which is the refrigerant upstream region of the dew condensation
preventive pipe 22B. The three way valve 29 is operated by a
controller 50 based on the refrigerant temperature detected by the
refrigerant temperature sensor 13. In consequence, it is controlled
whether to pass the refrigerant from the refrigerant pipe 22A which
is the refrigerant upstream region of the condenser 22 through the
dew condensation preventive pipe 22B or the bypass pipe 28.
[0070] Specifically, the controller 50 usually controls the three
way valve 29 so that the refrigerant from the refrigerant pipe 22A
constituting the refrigerant upstream region of the condenser 22
flows through the dew condensation preventive pipe 22B. Moreover,
when the refrigerant temperature detected by the refrigerant
temperature sensor 13 rises to a predetermined upper limit value
set beforehand, the three way valve 29 is switched so that the
refrigerant from the refrigerant pipe 22A constituting the
refrigerant upstream region of the condenser 22 flows through the
bypass pipe 28. Moreover, after elapse of a predetermined time, the
three way valve 29 is switched so that the refrigerant from the
refrigerant pipe 22A constituting the refrigerant upstream region
of the condenser 22 flows through the dew condensation preventive
pipe 22B.
[0071] In a case where the refrigerant temperature detected by the
refrigerant temperature sensor 13 rises to a predetermined upper
limit value, when the refrigerant is not passed through the dew
condensation preventive pipe 22B, and is passed through the bypass
pipe 28, the excessive temperature rise of the dew condensation
preventive pipe 22B can be prevented. In consequence, it is
possible to avoid in advance a disadvantage that owing to the
excessive temperature rise of the dew condensation preventive pipe
22B, a feeling of discomfort is given to a user or the user touches
the pipe to get burnt. In addition, safety of the refrigerator 1
can be secured.
[0072] It is to be noted that in the present embodiment, it has
been described that the refrigerant temperature sensor 13 for
detecting the temperature of the refrigerant flowing through the
dew condensation preventive pipe 22B is disposed at the inlet of
the dew condensation preventive pipe 22B or the outlet of the
refrigerant pipe 22A of the condenser 22 constituting the
refrigerant upstream region of the dew condensation preventive pipe
22B. A refrigerant channel is controlled so as to pass the
refrigerant through the dew condensation preventive pipe 22B or the
bypass pipe 28 based on the refrigerant temperature detected by the
refrigerant temperature sensor 13. However, the present invention
is not limited to this embodiment. The refrigerant channel may be
controlled based on, for example, the number of rotations of a
compressor 21, or the refrigerant may be passed through the bypass
pipe 28 during pull-down of the compressor 21 or for a
predetermined time.
* * * * *