U.S. patent application number 14/366251 was filed with the patent office on 2014-12-11 for refrigeration apparatus.
The applicant listed for this patent is KAIKIN INDUSTRIES, LTD.. Invention is credited to Noriyuki Okuda, Takamune Okui, Takayuki Setoguchi, Junichi Shimoda, Keisuke Tanimoto, Tsuyoshi Yamada.
Application Number | 20140360223 14/366251 |
Document ID | / |
Family ID | 48668522 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140360223 |
Kind Code |
A1 |
Setoguchi; Takayuki ; et
al. |
December 11, 2014 |
REFRIGERATION APPARATUS
Abstract
In an air-conditioning apparatus, refrigerant flows sequentially
through a compressor, an outdoor heat exchanger, expansion
mechanisms, and an indoor heat exchanger during a cooling
operation, and refrigerant flows sequentially through the
compressor, the indoor heat exchanger, the expansion mechanisms,
and the outdoor heat exchanger during a heating operation. Capacity
of the outdoor heat exchanger is 30% to 90% of the indoor heat
exchanger. The expansion mechanisms include an upstream-side and
downstream-side expansion mechanisms depressurizing refrigerant
from high to intermediate pressure, and from intermediate to low
pressure in the refrigerant cycle, respectively. The refrigerant is
R32. A refrigerant storage tank that stores the intermediate
pressure refrigerant is provided between the upstream-side and
downstream side expansion mechanisms. The refrigerant storage tank
stores an excess refrigerant produced during the cooling operation
due to capacity of the outdoor heat exchanger relative the indoor
heat exchanger.
Inventors: |
Setoguchi; Takayuki;
(Sakai-shi, JP) ; Tanimoto; Keisuke; (Sakai-shi,
JP) ; Okuda; Noriyuki; (Sakai-shi, JP) ; Okui;
Takamune; (Sakai-shi, JP) ; Shimoda; Junichi;
(Sakai-shi, JP) ; Yamada; Tsuyoshi; (Sakai-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KAIKIN INDUSTRIES, LTD. |
Osaka |
|
JP |
|
|
Family ID: |
48668522 |
Appl. No.: |
14/366251 |
Filed: |
December 19, 2012 |
PCT Filed: |
December 19, 2012 |
PCT NO: |
PCT/JP2012/082912 |
371 Date: |
June 17, 2014 |
Current U.S.
Class: |
62/509 |
Current CPC
Class: |
F25B 39/00 20130101;
F25B 1/005 20130101; F25B 13/00 20130101; F25B 2313/02741 20130101;
F25B 2400/12 20130101; F25B 43/00 20130101; F25B 29/003 20130101;
F25B 2400/23 20130101; F25B 2400/13 20130101; F25B 2313/0314
20130101; F25B 2341/0662 20130101 |
Class at
Publication: |
62/509 |
International
Class: |
F25B 29/00 20060101
F25B029/00; F25B 43/00 20060101 F25B043/00; F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2011 |
JP |
2011-278427 |
Mar 28, 2012 |
JP |
2012-074660 |
Claims
1. A refrigeration apparatus in which a refrigerant flows
sequentially through a compressor, an outdoor heat exchanger,
expansion mechanisms, and an indoor heat exchanger during a cooling
operation, and the refrigerant flows sequentially through the
compressor, the indoor heat exchanger, the expansion mechanisms,
and the outdoor heat exchanger during a heating operation; the
indoor heat exchanger being a cross-fin heat exchanger and the
outdoor heat exchanger being a stacked heat exchanger, and a
capacity ratio of the outdoor heat, exchanger to the indoor heat
exchanger is 0.3 to 0.9; the expansion mechanisms including an
upstream-side expansion mechanism configured to depressurize the
refrigerant from a high pressure in a refrigerant cycle to an
intermediate pressure in the refrigerant cycle and a
downstream-side expansion mechanism configured to depressurize the
refrigerant that has been depressurized in the upstream-side
expansion mechanism from the intermediate pressure in the
refrigerant cycle to a low pressure in the refrigerant cycle; the
outdoor heat exchanger, the upstream-side expansion mechanism and
the downstream-side expansion mechanism being provided in an
outdoor unit, the indoor heat exchanger being provided in an indoor
unit, and the outdoor unit and the indoor unit being connected via
a liquid refrigerant communication tube; the refrigerant being R32;
a refrigerant storage tank configured and arranged to store the
refrigerant depressurized to the intermediate pressure in the
refrigerant cycle by the upstream-side expansion mechanism being
provided between the upstream-side expansion mechanism and the
downstream -side expansion mechanism; and the refrigerant storage
tank storing an excess refrigerant produced during the cooling
operation due to a capacity of the outdoor heat exchanger being
less than a capacity of the indoor heat exchanger.
2. A refrigeration apparatus in which a refrigerant flows
sequentially through a compressor, an outdoor heat exchanger,
expansion mechanisms, and an indoor heat exchanger during a cooling
operation, and the refrigerant flows sequentially through the
compressor, the indoor heat exchanger, the expansion mechanisms,
and the outdoor heat exchanger during a heating operation; a
capacity of the outdoor heat exchanger being 30% to 90% of a
capacity of the indoor heat exchanger; the expansion mechanisms
including an upstream-side expansion mechanism, configured to
depressurize the refrigerant from a high pressure in a refrigerant
cycle to an intermediate pressure in the refrigerant cycle and a
downstream-side expansion mechanism configured to depressurize the
refrigerant that has been depressurized in the upstream-side
expansion mechanism from the intermediate pressure in the
refrigerant cycle to a low pressure in the refrigerant cycle; the
outdoor heat exchanger, the upstream-side expansion mechanism and
the downstream-side expansion mechanism being provided in an
outdoor unit, the indoor heat exchanger being provided in an indoor
unit, and the outdoor unit and the indoor unit being connected via
a liquid refrigerant communication tube; the refrigerant being R32;
a refrigerant storage tank configured and arranged to store the
refrigerant depressurized to the intermediate pressure in the
refrigerant cycle by the upstream-side expansion mechanism being
provided between the upstream-side expansion mechanism and the
downstream-side expansion mechanism; and the refrigerant storage
tank boring an excess refrigerant produced during the cooling
operation due to a capacity of the outdoor heat exchanger being
less than a capacity of the indoor heat exchanger.
3. The refrigeration apparatus according to claim 2, wherein the
outdoor heat exchanger is a stacked heal exchanger having a
plurality of flat lubes arrayed so as to be superposed set apart by
gaps, and fins sandwiched between adjacent flat tubes.
4. The refrigeration apparatus according to claim 2, wherein the
outdoor heat exchanger is a stacked heat exchanger having a
plurality of flat tubes arrayed so as to be superposed set apart by
gaps, and fins having notches formed therein where the flat tubes
are inserted.
5. The refrigeration apparatus according to claim 2, wherein the
outdoor heat exchanger is a stacked heat exchanger having flat
tubes molded into serpentine shapes, and fins inserted between
mutually adjacent surfaces of the flat tubes.
6. The refrigeration apparatus according to claim 2, wherein the
outdoor heat exchanger and the indoor heat exchanger are cross-fin
heat exchangers; and a diameter of heat transfer tubes in the
outdoor heat exchanger is less than a diameter of heat transfer
tubes in the indoor heat exchanger.
7. The refrigeration apparatus according to claim 2, further
comprising a bypass tube configured and arranged to lead a gas
component of the refrigerant accumulated in the refrigerant storage
tank to the compressor or to a refrigerant tube on an intake side
of the compressor.
8. The refrigeration apparatus according to claim 7, wherein the
bypass tube has a flow rate adjustment mechanism.
9. The refrigeration apparatus according to claim 2, wherein the
refrigerant storage tank is a gas-liquid separator.
10. The refrigeration apparatus according to claim 1, wherein the
outdoor heat exchanger is a stacked heat exchanger having a
plurality of flat tubes arrayed so as to be superposed set apart by
gaps, and fins sandwiched between adjacent flat tubes.
11. The refrigeration apparatus according to claim 1, wherein the
outdoor heat exchanger is a slacked heat exchanger having a
plurality of flat tubes arrayed so as to be superposed set apart by
gaps, and fins having notches formed therein where the flat tubes
are inserted.
12. The refrigeration apparatus according to claim 1, wherein the
outdoor heat exchanger is a stacked heat exchanger having flat
tubes molded into serpentine shapes, and fins inserted between
mutually adjacent surfaces of the flat tubes.
13. The refrigeration apparatus according to claim 1, further
comprising a bypass tube configured and arranged to lead a gas
component of the refrigerant accumulated in the refrigerant storage
tank to the compressor or to a refrigerant tube on an intake side
of the compressor.
14. The refrigeration apparatus according to claim 13, wherein the
bypass tube has a flow rate adjustment mechanism.
15. The refrigeration apparatus according to claim 1, wherein the
refrigerant storage tank is a gas-liquid separator.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigeration apparatus,
and particularly relates to a refrigeration apparatus capable of
performing a cooling operation and a heating operation.
BACKGROUND ART
[0002] In conventional refrigeration apparatuses such as
air-conditioning apparatuses capable of air-cooling and air-warming
operations, there is a difference between the optimal refrigerant
quantity for an air-cooling operation (cooling operation) and the
optimal refrigerant quantity for an air-warming operation (heating
operation). Accordingly, there is a difference between the capacity
of an outdoor heat exchanger functioning as a heat radiator of
refrigerant during the air-cooling operation and the capacity of an
indoor heat exchanger functioning as a heat radiator of refrigerant
during the air-warming operation. Because the capacity of the
outdoor heat exchanger is greater than the capacity of the indoor
heat exchanger, refrigerant that cannot be accommodated by the
indoor heat exchanger during the air-warming operation is
temporarily stored in a refrigerant storage tank or the like
connected to an intake side of a compressor.
SUMMARY OF THE INVENTION
[0003] However, in the refrigeration apparatus described above,
when a high-performance heat exchanger such as the one disclosed in
Patent Literature 1 (Japanese Laid-open Patent Application No.
6-143991) is used as an outdoor heat exchanger, the capacity of the
outdoor heat exchanger becomes equal to or less than the capacity
of the indoor heat exchanger. Therefore, in this case, refrigerant
that cannot be accommodated in the outdoor heat exchanger during
the air-cooling operation (excess refrigerant) is produced, and the
quantity of this refrigerant exceeds the quantity that can be
stored in the refrigerant storage tank or the like.
[0004] An object of the present invention is to provide a
refrigeration apparatus capable of performing a cooling operation
and a heating operation, wherein the excess refrigerant produced
during the cooling operation can be accommodated when the capacity
of the outdoor heat exchanger is equal to or less than the capacity
of the indoor heat exchanger.
[0005] A refrigeration apparatus according to a first aspect is a
refrigeration apparatus in which a refrigerant flows sequentially
through a compressor, an outdoor heat exchanger, expansion
mechanisms, and an indoor heat exchanger during a cooling
operation, and the refrigerant flows sequentially through the
compressor, the indoor heat exchanger, the expansion mechanisms,
and the outdoor heat exchanger during a heating operation. In this
refrigeration apparatus, the indoor heat exchanger is a cross-fin
type heat exchanger and the outdoor heat exchanger is a stacked
heat exchanger. Moreover, the expansion mechanisms include an
upstream-side expansion mechanism for depressurizing the
refrigerant and a downstream-side expansion mechanism for
depressurizing the refrigerant that has been depressurized in the
upstream-side expansion mechanism, and a refrigerant storage tank
for storing the refrigerant depressurized by the upstream-side
expansion mechanism is provided between the upstream-side expansion
mechanism and the downstream-side expansion mechanism.
[0006] A capacity of a stacked heat exchanger is less than a
capacity of a cross-fin type heat exchanger having similar heat
exchange performance. In a case of a refrigeration apparatus in
which the outdoor heat exchanger and the indoor heat exchanger are
both cross-fin type heat exchangers, and then only the outdoor heat
exchanger is changed to a stacked heat exchanger having similar
heat exchange performance, the capacity of this stacked outdoor
heat exchanger will then not only be less than the capacity of a
cross-fin type outdoor heat-exchanger, but will also be less than
the capacity of the cross-fin type indoor heat exchanger connected
thereto.
[0007] Therefore, in such a refrigeration apparatus, an excess
refrigerant is produced during the cooling operation due to the
capacity of the outdoor heat exchanger being less than the capacity
of the indoor heat exchanger. There is a risk that a refrigerant
control will be hindered when too much of this excess refrigerant
spreads from the indoor heat exchanger having a gas-phase portion
to portions as far as an intake side of the compressor.
[0008] In view of this, the refrigerant storage tank for storing
the refrigerant depressurized by the upstream-side expansion
mechanism is provided between the upstream-side expansion mechanism
and the downstream-side expansion mechanism, and the excess
refrigerant that could not be accommodated in the outdoor heat
exchanger during the cooling operation is thereby accommodated in
the refrigerant storage tank positioned in the vicinity of the
downstream side of the outdoor heat exchanger.
[0009] It is thereby possible to prevent hindrances to the
refrigerant control in this refrigeration apparatus, because it is
possible to prevent too much refrigerant from spreading from the
indoor heat exchanger having a gas-phase portion to portions as far
as the intake side of the compressor.
[0010] A refrigeration apparatus according to a second aspect is a
refrigeration apparatus in which a refrigerant flows sequentially
through a compressor, an outdoor heat exchanger, expansion
mechanisms, and an indoor heat exchanger during a cooling
operation, and refrigerant flows sequentially through the
compressor, the indoor heat exchanger, the expansion mechanisms,
and the outdoor heat exchanger during a heating operation. In this
refrigeration apparatus, a capacity of the outdoor heat exchanger
is 100% or less of a capacity of the indoor heat exchanger.
Moreover, the expansion mechanisms include an upstream-side
expansion mechanism for depressurizing the refrigerant and a
downstream-side expansion mechanism for depressurizing the
refrigerant that has been depressurized in the upstream-side
expansion mechanism, and a refrigerant storage tank for storing the
refrigerant depressurized by the upstream-side expansion mechanism
is provided between the upstream-side expansion mechanism and the
downstream-side expansion mechanism.
[0011] When the capacity of the outdoor heat exchanger is equal to
or less than the capacity of the indoor heat exchanger, an excess
refrigerant is produced during the cooling operation. There is a
risk that a refrigerant control will be hindered when too much of
this excess refrigerant spreads from the indoor heat exchanger
having a gas-phase portion to portions as far as an intake side of
the compressor.
[0012] In view of this, the refrigerant storage tank for storing
the refrigerant depressurized by the upstream-side expansion
mechanism is provided between the upstream-side expansion mechanism
and the downstream-side expansion mechanism, and the excess
refrigerant that could not be accommodated in the outdoor heat
exchanger during the cooling operation is thereby accommodated in
the refrigerant storage tank positioned in the vicinity of the
downstream side of the outdoor heat exchanger.
[0013] It is thereby possible to prevent hindrances to the
refrigerant control in this refrigeration apparatus, because it is
possible to prevent too much refrigerant from spreading from the
indoor heat exchanger having a gas-phase portion to portions as far
as the intake side of the compressor.
[0014] A refrigeration apparatus according to a third aspect is the
refrigeration apparatus according to the first or second aspect,
wherein the refrigerant is R32.
[0015] When R32 is used as the refrigerant in the refrigeration
apparatus, a refrigerator oil sealed with the refrigerant in order
to lubricate the compressor tends to have extremely low solubility
in low-temperature conditions. Therefore, at a low pressure in the
refrigeration cycle, the solubility of the refrigerator oil greatly
decreases due to the decrease in a refrigerant temperature. When
R32 is used as the refrigerant in a conventional refrigeration
apparatus having the refrigerant storage tank on the intake side of
the compressor, for example, the refrigerant and the refrigerator
oil separate into two layers in the refrigerant storage tank which
has a low pressure in the refrigeration cycle, and the refrigerator
oil has difficulty returning to the compressor.
[0016] However, because the refrigerant storage tank is provided
between the upstream-side expansion mechanism and the
downstream-side expansion mechanism in this refrigeration apparatus
as described above, the refrigerator oil returns more readily to
the compressor, in comparison to cases in which the refrigerant
storage tank is provided to the intake side of the compressor.
[0017] Thus, in this refrigeration apparatus, due to the
refrigerant storage tank being provided between the upstream-side
expansion mechanism and the downstream-side expansion mechanism, it
is possible to resolve not only the problem of the excess
refrigerant produced by the capacity of the outdoor heat exchanger
being equal to or less than the capacity of the indoor heat
exchanger, due to factors such as a stacked heat exchanger being
used as the outdoor heat exchanger, but also the problem of oil
returning to the compressor, caused by using R32 as the
refrigerant.
[0018] A refrigeration apparatus according to a fourth aspect is
the refrigeration apparatus according to any of the first through
third aspects, wherein the outdoor heat exchanger is a stacked heat
exchanger having a plurality of flat tubes arrayed so as to be
superposed set apart by gaps, and fins sandwiched between the
adjacent flat tubes.
[0019] In this refrigeration apparatus, similar to the
refrigeration apparatus according to the first through third
aspects described above, the refrigerant quantity in the
refrigeration apparatus is reduced because the capacity of the
outdoor heat exchanger is equal to or less than the capacity of the
indoor heat exchanger. The excess refrigerant is produced during
the cooling operation in this refrigeration apparatus, but because
this excess refrigerant can be accommodated in the refrigerant
storage tank, hindrances to the refrigerant control can be
prevented.
[0020] A refrigeration apparatus according to a fifth aspect is the
refrigeration apparatus according to any of the first through third
aspects, wherein the outdoor heat exchanger is a stacked heat
exchanger having a plurality of flat tubes arrayed so as to be
superposed set apart by gaps, and fins having notches formed
therein where the flat tubes are inserted.
[0021] In this refrigeration apparatus, similar to the
refrigeration apparatus according to the first through third
aspects described above, the refrigerant quantity in the
refrigeration apparatus is reduced because the capacity of the
outdoor heat exchanger is equal to or less than the capacity of the
indoor heat exchanger. The excess refrigerant is produced during
the cooling operation in this refrigeration apparatus, but because
this excess refrigerant can be accommodated in the refrigerant
storage tank, hindrances to the refrigerant control can be
prevented.
[0022] A refrigeration apparatus according to a sixth aspect is the
refrigeration apparatus according to any of the first through third
aspects, wherein the outdoor heat exchanger is a stacked heat
exchanger having flat tubes molded into serpentine shapes, and fins
inserted between mutually adjacent surfaces of the flat tubes.
[0023] In this refrigeration apparatus, similar to the
refrigeration apparatus according to the first or second aspect
described above, the refrigerant quantity in the refrigeration
apparatus is reduced because the capacity of the outdoor heat
exchanger is equal to or less than the capacity of the indoor heat
exchanger. The excess refrigerant is produced during the cooling
operation in this refrigeration apparatus, but because this excess
refrigerant can be accommodated in the refrigerant storage tank,
hindrances to the refrigerant control can be prevented.
[0024] A refrigeration apparatus according to a seventh aspect is
the refrigeration apparatus according to the second aspect, wherein
the refrigerant is R32.
[0025] When R32 is used as the refrigerant in the refrigeration
apparatus, a refrigerator oil sealed with the refrigerant in order
to lubricate the compressor tends to have extremely low solubility
in low-temperature conditions. Therefore, at a low pressure in the
refrigeration cycle, the solubility of the refrigerator oil greatly
decreases due to the decrease in a refrigerant temperature. When
R32 is used as the refrigerant in a conventional refrigeration
apparatus having the refrigerant storage tank on the intake side of
the compressor, for example, the refrigerant and the refrigerator
oil separate into two layers in the refrigerant storage tank which
has a low pressure in the refrigeration cycle, and the refrigerator
oil has difficulty returning to the compressor.
[0026] However, because the refrigerant storage tank is provided
between the upstream-side expansion mechanism and the
downstream-side expansion mechanism in this refrigeration apparatus
as described above, the refrigerator oil returns more readily to
the compressor, in comparison to cases in which the refrigerant
storage tank is provided to the intake side of the compressor.
[0027] Thus, in this refrigeration apparatus, due to the
refrigerant storage tank being provided between the upstream-side
expansion mechanism and the downstream-side expansion mechanism, it
is possible to resolve not only the problem of the excess
refrigerant produced by the capacity of the outdoor heat exchanger
being equal to or less than the capacity of the indoor heat
exchanger, but also the problem of oil returning to the compressor,
caused by using R32 as the refrigerant.
[0028] A refrigeration apparatus according to an eighth aspect is
the refrigeration apparatus according to the second or seventh
aspect, wherein the outdoor heat exchanger and the indoor heat
exchanger are cross-fin type heat exchangers, and a diameter of
heat transfer tubes in the outdoor heat exchanger is designed to be
less than a diameter of heat transfer tubes in the indoor heat
exchanger.
[0029] In this refrigeration apparatus, similar to the
refrigeration apparatus according to the second aspect described
above, the refrigerant quantity in the refrigeration apparatus is
reduced because the capacity of the outdoor heat exchanger is equal
to or less than the capacity of the indoor heat exchanger. The
excess refrigerant is produced during the cooling operation in this
refrigeration apparatus, but because this excess refrigerant can be
accommodated in the refrigerant storage tank, hindrances to the
refrigerant control can be prevented.
[0030] A refrigeration apparatus according to a ninth aspect is the
refrigeration apparatus according to any of the first through
eighth aspects, further provided with a bypass tube for leading a
gas component of the refrigerant accumulated in the refrigerant
storage tank to the compressor or to a refrigerant tube on an
intake side of the compressor.
[0031] In this refrigeration apparatus, the refrigerant
depressurized in the upstream-side expansion mechanism is separated
into a liquid component and the gas component in the refrigerant
storage tank, and the gas component heads toward the bypass
tube.
[0032] The gas component, which does not contribute to evaporation,
thereby ceases to flow into the outdoor heat exchanger functioning
as an evaporator of the refrigerant during the heating operation in
this refrigeration apparatus, it is therefore possible to
proportionately reduce the flow rate of the refrigerant flowing
through the outdoor heat exchanger functioning as an evaporator of
the refrigerant, and a depressurization loss in the refrigeration
cycle can be reduced.
[0033] A refrigeration apparatus according to a tenth aspect is the
refrigeration apparatus according to the ninth aspect, wherein the
bypass tube has a flow rate adjustment mechanism.
[0034] When the operating frequency of the compressor is high,
there is a risk that a gas-liquid two-phase refrigerant from the
refrigerant storage tank will pass through the bypass tube, return
to the compressor or the intake tube of the compressor, and be
drawn into the compressor.
[0035] However, in this refrigeration apparatus, because the flow
rate adjustment mechanism is provided to the bypass tube, the
liquid component of the gas-liquid two-phase refrigerant is
depressurized and evaporated.
[0036] It is thereby possible in this refrigeration apparatus to
prevent the liquid component from returning to the compressor or
the intake tube of the compressor.
[0037] During the heating operation in this refrigeration
apparatus, the refrigerant that has passed through the flow rate
adjustment mechanism converges with the refrigerant which has
evaporated in the outdoor heat exchanger, and then heads to the
compressor or the intake tube of the compressor. At this time, in
the case that the flow rate adjustment mechanism is an electric
expansion valve, the state of the refrigerant just before being
drawn into the compressor can be adjusted more optimally by
controlling the valve opening degree. Moreover, because the flow
rate of the refrigerant returning to the compressor can be
increased or reduced by controlling the valve opening degree of the
flow rate adjustment mechanism, the refrigerant circulation flow
rate, i.e. the flow rate of the refrigerant flowing through the
indoor heat exchanger can be controlled according to the
refrigeration load on the indoor heat exchanger side.
[0038] A refrigeration apparatus according to an eleventh aspect is
the refrigeration apparatus according to any of the first through
tenth aspects, wherein the refrigerant storage tank is a gas-liquid
separator.
[0039] In this refrigeration apparatus, the refrigerant storage
tank composed of the gas-liquid separator has both a function of
accumulating a liquid component and a function of separating the
liquid component and a gas component.
[0040] This contributes to simplifying the apparatus configuration
in this refrigeration apparatus because there is no need to provide
both a container having a refrigerant storage function and a
container having a gas-liquid separating function.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a schematic configuration diagram of an air
conditioning apparatus as a refrigeration apparatus according to an
embodiment of the present invention.
[0042] FIG. 2 is a schematic front view of an indoor heat
exchanger.
[0043] FIG. 3 is an external perspective view of an outdoor heat
exchanger.
[0044] FIG. 4 is a graph showing the outdoor heat exchanger
capacity/indoor heat exchanger capacity ratio according to
capability.
[0045] FIG 5 is a schematic cross-sectional view of a refrigerant
storage tank in Modification 1.
[0046] FIG. 6 is an external perspective view of an outdoor heat
exchanger in Modification
[0047] FIG. 7 is a longitudinal cross-sectional view of the outdoor
heat exchanger in Modification 2.
DESCRIPTION OF EMBODIMENTS
[0048] An embodiment of the refrigeration apparatus according to
the present invention and modifications thereof are described below
with reference to the drawings. The specific configuration of the
refrigeration apparatus according to the present invention is not
limited to the following embodiment or the modifications thereof,
and can be altered within a range that does not deviate from the
scope of the invention.
[0049] (1) Configuration of Air-Conditioning Apparatus
[0050] FIG. 1 is a schematic configuration diagram of an
air-conditioning apparatus 1 as a refrigeration apparatus according
to an embodiment of the present invention.
[0051] The air-conditioning apparatus 1 is a refrigeration
apparatus capable of performing an air-cooling operation as a
cooling operation and an air-warming operation as a heating
operation by performing a vapor-compression refrigeration cycle.
The air-conditioning apparatus 1 is configured primarily from the
connection between an outdoor unit 2 and an indoor unit 4. The
outdoor unit 2 and the indoor unit 4 are connected via a liquid
refrigerant communication tube 5 and a gas refrigerant
communication tube 6. Specifically, a vapor-compression refrigerant
circuit 10 of the air-conditioning apparatus 1 is configured from
the connection between the outdoor unit 2 and the indoor unit 4 via
the refrigerant communication tubes 5, 6.
[0052] <Indoor Unit>
[0053] The indoor unit 4, which is installed inside a room,
constitutes part of the refrigerant circuit 10. he indoor unit 4
primarily has an indoor heat exchanger 41.
[0054] The indoor heat exchanger 41 is a heat exchanger that
functions as an evaporator of refrigerant to cool indoor air during
the air-cooling operation, and functions as a heat radiator of
refrigerant during the air-warming operation to heat indoor air. A
liquid side of the indoor heat exchanger 41 is connected to the
liquid refrigerant communication tube 5, and a gas side of the
indoor heat exchanger 41 is connected to the gas refrigerant
communication tube 6.
[0055] The indoor heat exchanger 41, which is a cross-fin type heat
exchanger, has primarily heat transfer fins 411 and heat transfer
tubes 412, as shown in FIG. 2. FIG 2 is a front view of the indoor
heat exchanger 41. The heat transfer fins 411 are thin aluminum
flat plates, and pluralities of through-holes are formed in the
heat transfer fins 411. The heat transfer tubes 412 have straight
tubes 412a inserted through the through-holes of the heat transfer
fins 411, and U-shaped tubes 412b, 412c linking the ends of
adjacent straight tubes 412a together. The straight tubes 412a are
firmly adhered to the heat transfer fins 411 by undergoing an
expanding process after being inserted through the through-holes of
the heat transfer fins 411. The straight tubes 412a and the first
U-shaped tubes 412b are formed integrally, and the second U-shaped
tubes 412c are linked to the ends of the straight tubes 412a by
welding, soldering, or the like, after being inserted through the
through-holes of the heat transfer fins 411 and undergoing the
expanding process.
[0056] The indoor unit 4 also has an indoor fan 42 for drawing
indoor air into the indoor unit 4 and supplying the air back into
the room as supplied air after the air has exchanged heat with the
refrigerant in the indoor heat exchanger 41. The indoor fan 42 is a
centrifugal fan, a multi-blade fan, or the like driven by an indoor
fan motor 43.
[0057] The indoor unit 4 has an indoor-side control part 44 for
controlling the actions of the components constituting the indoor
unit 4. The indoor-side control part 44, which has a microcomputer,
a memory, and the like for performing control on the indoor unit 4,
is designed to be capable of exchanging control signals and the
like with a remote controller (not shown), and also of exchanging
control signals and the like with the outdoor unit 2 via a
transmission line 8a.
[0058] <Outdoor Unit>
[0059] The outdoor unit 2, which is installed outside of the room,
constitutes part of the refrigerant circuit 10. The outdoor unit 2
has primarily a compressor 21, a switching mechanism 22, an outdoor
heat exchanger 23, a first expansion mechanism 24, a refrigerant
storage tank 25, a second expansion mechanism 26, a liquid-side
shutoff valve 27, and a gas-side shutoff valve 28.
[0060] The compressor 21 is a device for compressing low-pressure
refrigerant in the refrigeration cycle to a high pressure. The
compressor 21 has a sealed structure in which a rotary, scroll, or
other type of displacement compression element (not shown) is
rotatably driven by a compressor motor 21a controlled by an
inverter. An intake tube 31 is connected to the intake side of the
compressor 21, and a discharge tube 32 is connected to the
discharge side. The intake tube 31 is a refrigerant tube connecting
the intake side of the compressor 21 and a first port 22a of the
switching mechanism 22. An accumulator 29 is provided to the intake
tube 31. The discharge tube 32 is a refrigerant tube connecting the
discharge side of the compressor 21 and a second port 22b of the
switching mechanism 22.
[0061] The switching mechanism 22 is a mechanism for switching the
direction of refrigerant flow in the refrigerant circuit 10. During
the air-cooling operation, the switching mechanism 22 performs a
switch that causes the outdoor heat exchanger 23 to function as a
heat radiator of refrigerant compressed in the compressor 21, and
causes the indoor heat exchanger 41 to function as an evaporator of
refrigerant that has radiated heat in the outdoor heat exchanger
23. Specifically, during the air-cooling operation, the switching
mechanism 22 performs a switch that interconnects the second port
22b and a third port 22c, and interconnects the first port 22a and
a fourth port 22d. The discharge side of the compressor 21 (the
discharge tube 32 herein) and the gas side of the outdoor heat
exchanger 23 (a first gas refrigerant tube 33 herein) are thereby
connected (refer to the solid lines of the switching mechanism 22
in FIG. 1). Moreover, the intake side of the compressor 21 (the
intake tube 31 herein) and the gas refrigerant communication tube 6
side (a second gas refrigerant tube 34 herein) are connected (refer
to the solid lines of the switching mechanism 22 in FIG. 1). During
the air-warming operation, the switching mechanism 22 performs a
switch that causes the outdoor heat exchanger 23 to function as an
evaporator of refrigerant that has radiated heat in the indoor heat
exchanger 41, and causes the indoor heat exchanger 41 to function
as a heat radiator of refrigerant that has been compressed in the
compressor 21. Specifically, during the air-warming operation, the
switching mechanism 22 performs a switch that interconnects the
second port 22b and the fourth port 22d, and interconnects the
first port 22a and the third port 22c. The discharge side of the
compressor 21 (the discharge tube 32 herein) and the gas
refrigerant communication tube 6 side (the second gas refrigerant
tube 34 herein) are thereby connected (refer to the dashed lines of
the switching mechanism 22 in FIG. 1). Moreover, the intake side of
the compressor 21 (the intake tube 31 herein) and the gas side of
the outdoor heat exchanger 23 (the first gas refrigerant tube 33
herein) are connected (refer to the dashed lines of the switching
mechanism 22 in FIG. 1). The first gas refrigerant tube 33 is a
refrigerant tube connecting the third port 22c of the switching
mechanism 22 and the gas side of the outdoor heat exchanger 23. The
second gas refrigerant tube 34 is a refrigerant tube connecting the
fourth port 22d of the switching mechanism 22 and the gas
refrigerant communication tube 6 side. The switching mechanism 22
herein is a four-way switching valve.
[0062] The outdoor heat exchanger 23 is a heat exchanger that
functions as a heat radiator of refrigerant that uses outdoor air
as a cooling source during the air-cooling operation, and functions
as an evaporator of refrigerant that uses outdoor air as a heating
source during the air-warming operation. The liquid side of the
outdoor heat exchanger 23 is connected to a liquid refrigerant tube
35, and the gas side is connected to the first gas refrigerant tube
33. The liquid refrigerant tube 35 is a refrigerant tube connecting
the liquid side of the outdoor heat exchanger 23 and the liquid
refrigerant communication tube 5 side.
[0063] The outdoor heat exchanger 23, which is a stacked heat
exchanger, has primarily flat tubes 231, corrugated fins 232, and
headers 233a, 233b, as shown in FIG. 3. FIG. 3 is an external
perspective view of the outdoor heat exchanger 23. The flat tubes
231, which are molded from aluminum or an aluminum alloy, have flat
surface parts 231a that serve as heat transfer surfaces and a
plurality of internal flow channels (not shown) through which
refrigerant flows. The flat tubes 231 are arrayed in multiple
levels so as to be superposed set apart by gaps (air passage
spaces) with the flat surface parts 231a being made to face up and
down. The corrugated fins 232 are fins made of aluminum or an
aluminum alloy, bent into a corrugated formation. The corrugated
fins 232 are disposed in air passage spaces enclosed between
vertically adjacent flat tubes 231, and the troughs and peaks
thereof are in contact with the flat surface parts 231a of the flat
tubes 231. The troughs, peaks, and flat surface parts 231a are
bonded by soldering or the like. The headers 233a, 233b are linked
to the ends of the flat tubes 231 arrayed in multiple levels in the
vertical direction. The headers 233a, 233b have the function of
supporting the flat tubes 231, the function of leading refrigerant
into the internal flow channels of the flat tubes 231, and the
function of collecting refrigerant coming out of the internal flow
channels. When the outdoor heat exchanger 23 functions as a heat
radiator of refrigerant, refrigerant flowing in through a first
inlet/outlet 234 of the first header 233a is distributed mostly
equally to the internal flow channels of the topmost flat tube 231,
and the refrigerant flows toward the second header 233b, Having
reached the second header 233b, the refrigerant is distributed
mostly equally to the infernal flow channels of the second highest
flat tube 231, and the refrigerant flows toward the first header
233a. The refrigerant in the flat tubes 231 of odd-numbered levels
flows toward the second header 233b, and the refrigerant in the
flat tubes 231 of even-numbered levels flows toward the first
header 233a. The refrigerant in the bottommost and even-numbered
level flat tubes 231 flows toward the first header 233a, collects
in the first header 233a, and flows out through a second
inlet/outlet 235 of the first header 233a. When the outdoor heat
exchanger 23 functions as an evaporator of refrigerant, refrigerant
flows in through the second inlet/outlet 235 of the first header
233a, and after flowing through the flat tubes 231 and the headers
233a, 233b in the opposite direction of when the outdoor heat
exchanger functions as a heat radiator of refrigerant, the
refrigerant flows out through the first inlet/outlet 234 of the
first header 233a. When the outdoor heat exchanger 23 functions as
a heat radiator of refrigerant, the refrigerant flowing in the flat
tubes 231 radiates heat to the air flow passing through the air
passage spaces via the corrugated fins 232. When the outdoor heat
exchanger 23 functions as an evaporator of refrigerant, the
refrigerant flowing in the flat tubes 231 absorbs heat from the air
flow passing through the air passage spaces via the corrugated fins
232. Due to a stacked heat exchanger such as the one described
above being used as the outdoor heat exchanger 23, the capacity of
the outdoor heat exchanger 23 is less than the capacity of the
indoor heat exchanger 41. This point is described using FIG. 4,
giving a package air-conditioner as an example. FIG. 4 is a graph
showing the outdoor heat exchanger capacity/indoor heat exchanger
capacity ratio according to capability. In FIG. 4, the symbol
.diamond. represents a normal type (a cross-fin type outdoor heat
exchanger) of a package air-conditioner, the symbol .diamond-solid.
represents a small diameter type of outdoor heat exchanger (a
stacked outdoor heat exchanger) of a package air-conditioner, the
symbol .DELTA. represents a normal type (a cross-fin type outdoor
heat exchanger) of a room air-conditioner, and the symbol
.tangle-solidup. represents a small diameter type of outdoor heat
exchanger (a stacked outdoor heat exchanger) of a room
air-conditioner. According to FIG. 4, the outdoor heat exchanger
capacity/indoor heat exchanger capacity ratio is less than 1.0 when
only the outdoor heat exchanger is changed to a stacked heat
exchanger having a similar heat exchange performance, in contrast
to when the outdoor heat exchanger and the indoor heat exchanger
are both cross-fin type heat exchangers. This means that not only
is the capacity of a stacked heat exchanger less than the capacity
of a cross-fin type outdoor heat exchanger, but it is also less
than the capacity of a cross-fin type indoor heat exchanger 41
connected thereto. Therefore, in the air-conditioning apparatus 1,
excess refrigerant is produced during the air-cooling operation. In
view of this, in the air-conditioning apparatus 1, the excess
refrigerant is accommodated in the refrigerant storage tank 25.
According to FIG. 4, the refrigerant storage tank 25 for
accommodating excess refrigerant is preferably used when the
outdoor heat exchanger capacity/indoor heat exchanger capacity
ratio is 0.3 to 0.9, but stable refrigerant control is made
possible by using the refrigerant storage tank 25 also when the
outdoor heat exchanger capacity/indoor heat exchanger capacity
ratio is 1.0.
[0064] During the air-cooling operation, the first expansion
mechanism 24 functions as an upstream-side expansion mechanism for
depressurizing the refrigerant that has radiated heat in the
outdoor heat exchanger 23 to an intermediate pressure in the
refrigeration cycle, and during the air-warming operation, the
first expansion mechanism 24 functions as a downstream-side
expansion mechanism for depressurizing the refrigerant temporarily
stored in the refrigerant storage tank 25 to a low pressure in the
refrigeration cycle after the refrigerant has been depressurized in
the second expansion mechanism 26 as an upstream-side expansion
mechanism. The first expansion mechanism 24 is provided to a
portion near the outdoor heat exchanger 23 in the liquid
refrigerant tube 35. An electric expansion valve is used herein as
the first expansion mechanism 24.
[0065] During the air-cooling operation, the second expansion
mechanism 26 functions as a downstream-side expansion mechanism for
depressurizing the refrigerant temporarily stored in the
refrigerant storage tank 25 to a low pressure in the refrigeration
cycle, after the refrigerant has been depressurized in the first
expansion mechanism 24 as an upstream-side expansion mechanism.
During the air-warming operation, the second expansion mechanism 26
functions as an upstream-side expansion mechanism for
depressurizing the refrigerant that has radiated heat in the indoor
heat exchanger 41 to an intermediate pressure in the refrigeration
cycle. The second expansion mechanism 26 is provided to a portion
of the liquid refrigerant tube 35 that is near the liquid-side
shutoff valve 27. An electric expansion valve is used herein as the
second expansion mechanism 26.
[0066] The refrigerant storage tank 25, which is provided between
the first expansion mechanism 24 and the second expansion mechanism
26, is a container that can collect refrigerant as excess
refrigerant, after the refrigerant has been depressurized by the
first expansion mechanism 24 or second expansion mechanism 26
functioning as an upstream-side expansion mechanism. For example,
in a case in which the liquid refrigerant quantity that can be
accommodated in the indoor heat exchanger 41 is 1100 cc during the
air-warming operation in which the indoor heat exchanger 41
functions as a heat radiator of refrigerant, and the liquid
refrigerant quantity that can be accommodated in the outdoor heat
exchanger 23 is 800 cc during the air-cooling operation in which
the outdoor heat exchanger 23 functions as a heat radiator of
refrigerant, 300 cc of leftover liquid refrigerant that could not
be accommodated in the outdoor heat exchanger 23 during the
air-cooling operation is temporarily accommodated in the
refrigerant storage tank 25. The refrigerant just before entering
the refrigerant storage tank 25, for example, also includes a gas
component produced when the refrigerant is depressurized in the
first expansion mechanism 24 or second expansion mechanism 26
functioning as an upstream-side expansion mechanism. Therefore, the
refrigerant is separated into a liquid component and a gas
component after entering the refrigerant storage tank 25, the
liquid refrigerant is stored in the downstream side, and the gas
component is stored in the upstream side. The gas refrigerant
separated in the refrigerant storage tank 25 passes through a
bypass tube 30 and flows to the intake tube 31 of the compressor
21. The liquid refrigerant separated in the refrigerant storage
tank 25 flows to the outdoor heat exchanger 23 after being
depressurized in the second expansion mechanism 26 or first
expansion mechanism 24 functioning as an upstream-side expansion
mechanism. The bypass tube 30 is provided so as to connect the top
part of the refrigerant storage tank 25 and the middle portion of
the intake tube 31. A flow rate adjustment mechanism 30a is
provided in the middle of the bypass tube 30. An electric expansion
valve is used herein as the flow rate adjustment mechanism 30a. The
outlet of the bypass tube 30 may also be connected directly to the
compressor 21, rather than being connected to the middle portion of
the intake tube 31.
[0067] The liquid-side shutoff valve 27 and the gas-side shutoff
valve 28 are valves provided to ports connecting with external
devices and tubing (specifically, the liquid refrigerant
communication tube 5 and the gas refrigerant communication tube 6).
The second expansion mechanism 26 is provided to an end of the
liquid refrigerant tube 35. The liquid-side shutoff valve 27 is
provided to an end of the second gas refrigerant tube 34.
[0068] The outdoor unit 2 has an outdoor fan 36 for drawing outdoor
air into the outdoor unit 2 and expelling the air to the exterior
after the air has undergone heat exchange with the refrigerant in
the outdoor heat exchanger 23. The outdoor fan 36 herein is a
propeller fan or the like driven by an outdoor fan motor 37.
[0069] The outdoor unit 2 has an outdoor-side control part 38 for
controlling the actions of the components constituting the outdoor
unit 2. The outdoor-side control part 38, which has a
microcomputer, a memory, and the like for performing control on the
outdoor unit 2, is designed to be capable of exchanging control
signals and the like with an indoor-side control part 44 of the
indoor unit 4 via the transmission line 8a. Specifically, a control
part 8 for performing the operation controls for the entire
air-conditioning apparatus 1 is configured by the indoor-side
control part 44, the outdoor-side control part 38, and the
transmission line 8a which connects the control parts 38, 44.
[0070] The control part 8 is designed to be capable of controlling
the actions of the various devices and valves 21a, 22, 24, 26, 30a,
37, 43, etc., on the basis of various operation settings, the
values detected by various sensors, and the like.
[0071] <Refrigerant Communication Tubes>
[0072] The refrigerant communication tubes 5, 6, which are
refrigerant tubes machined on-site when the air-conditioning
apparatus 1 is installed in an installation location such as a
building, have various lengths and/or tube diameters according to
the installation location and/or installation conditions such as
the combination of the outdoor unit and the indoor unit.
[0073] As described above, the refrigerant circuit 10 of the
air-conditioning apparatus 1 is configured from the connection
between the outdoor unit 2, the indoor unit 4, and the refrigerant
communication tubes 5, 6. During the air-cooling operation as a
cooling operation, the refrigerant circuit 10 is designed to
perform a refrigeration cycle in which refrigerant flows
sequentially through the compressor 21, the outdoor heat exchanger
23, the first expansion mechanism 24 as an upstream-side expansion
mechanism, the refrigerant storage tank 25, the second expansion
mechanism 26 as a downstream-side expansion mechanism, and the
indoor heat exchanger 41. During the air-warming operation as a
heating operation, the refrigerant circuit 10 is designed to
perform a refrigeration cycle in which refrigerant flows
sequentially through the compressor 21, the indoor heat exchanger
41, the second expansion mechanism 26 as an upstream-side expansion
mechanism, the refrigerant storage tank 25, the first expansion
mechanism 24 as a downstream-side expansion mechanism, and the
outdoor heat exchanger 23. The air-conditioning apparatus 1 is
designed to be capable of performing various operations such as the
air-cooling operation and the air-warming operation, by means of
the control part 8 configured from the indoor-side control part 44
and the outdoor-side control part 38.
[0074] (2) Actions of Air Conditioning Apparatus
[0075] The air-conditioning apparatus 1 can perform an air-cooling
operation and an air-warming operation as described above. The
actions of the air-conditioning apparatus 1 during the air-cooling
operation and the air-warming operation are described below.
[0076] <Air-Warming Operation>
[0077] During the air-warming operation, a switch is performed in
which the switching mechanism 22 is in the state shown by the
dashed lines in FIG. 1, i.e., the second port 22b and the fourth
port 22d are communicated, and the first port 22a and the third
port 22c are communicated.
[0078] In this refrigerant circuit 10, low-pressure refrigerant in
the refrigeration cycle is drawn into the compressor 21 and
discharged after being compressed to a high pressure.
[0079] The high-pressure refrigerant discharged from the compressor
21 is sent through the switching mechanism 22, the gas-side shutoff
valve 28, and the gas refrigerant communication tube 6 to the
indoor heat exchanger 41.
[0080] The high-pressure refrigerant sent to the indoor heat
exchanger 41 undergoes heat exchange with indoor air and radiates
heat in the indoor heat exchanger 41. The indoor air is thereby
heated. Because the capacity of the indoor heat exchanger 41 is
greater than the capacity of the outdoor heat exchanger 23, most of
the liquid refrigerant is accommodated in the indoor heat exchanger
41 during the air-warming operation.
[0081] The high-pressure refrigerant that has radiated heat in the
indoor heat exchanger 41 is sent through the liquid refrigerant
communication tube 5 and the liquid-side shutoff valve 27 to the
second expansion mechanism 26 functioning as an upstream-side
expansion mechanism.
[0082] The refrigerant sent to the second expansion mechanism 26 is
depressurized to an intermediate pressure by the second expansion
mechanism 26, and is then sent to the refrigerant storage tank 25.
The refrigerant just before entering the refrigerant storage tank
25 includes a gas component produced when the refrigerant is
depressurized in the second expansion mechanism 26, but after
entering the refrigerant storage tank 25, the refrigerant is
divided into a liquid component and a gas component, the liquid
refrigerant is stored in the lower side, and the gas refrigerant is
stored in the upper side. At this time, because the flow rate
adjustment mechanism 30a of the bypass tube 30 is controlled to an
open state, the gas refrigerant in the refrigerant storage tank 25
passes through the bypass tube 30 and heads to the intake tube 31
of the compressor 21. The liquid refrigerant in the refrigerant
storage tank 25 is sent to the outdoor heat exchanger 23 after
being depressurized to a low pressure by the first expansion
mechanism 24 functioning as a downstream-side expansion
mechanism.
[0083] The low-pressure refrigerant sent to the outdoor heat
exchanger 23 undergoes heat exchange with outdoor air supplied by
the outdoor fan 36 and evaporates in the outdoor heat exchanger 23.
At this time, the refrigerant flowing into the outdoor heat
exchanger 23 is reduced by the gas-liquid separating process in the
refrigerant storage tank 25, as well as the process of drawing the
gas-liquid separated gas refrigerant through the bypass tube 30
into the compressor 21. Therefore, the flow rate of refrigerant
flowing through the outdoor heat exchanger 23 decreases, pressure
loss can be reduced proportionately, and the depressurization loss
in the refrigeration cycle can therefore be reduced.
[0084] The low-pressure refrigerant evaporated in the outdoor heat
exchanger 23 is drawn through the switching mechanism 22 back into
the compressor 21.
[0085] <Air-Cooling Operation>
[0086] During the air-cooling operation, a switch is performed in
which the switching mechanism 22 is in the state shown by the solid
lines in FIG. 1, i.e., the second port 22b and the third port 22c
are communicated, and the first port 22a and the fourth port 22d
are communicated.
[0087] In this refrigerant circuit 10, low-pressure refrigerant in
the refrigeration cycle is drawn into the compressor 21 and
discharged after being compressed to a high pressure.
[0088] The high-pressure refrigerant discharged from the compressor
21 is sent through the switching mechanism 22 to the outdoor heat
exchanger 23.
[0089] The high-pressure refrigerant sent to the outdoor heat
exchanger 23 undergoes heat exchange with outdoor air and radiates
heat in the outdoor heat exchanger 23.
[0090] The high-pressure refrigerant that has radiated heat in the
outdoor heat exchanger 23 is sent to the first expansion mechanism
24 functioning as an upstream-side expansion mechanism,
depressurized to an intermediate pressure by the first expansion
mechanism 24, and then sent to the refrigerant storage tank 25.
Because the capacity of the outdoor heat exchanger 23 is equal to
or less than the capacity of the indoor heat exchanger 41 here, the
outdoor heat exchanger 23 is not able to accommodate all of the
liquid refrigerant during the air-cooling operation. Therefore, the
liquid refrigerant that could not be accommodated in the outdoor
heat exchanger 23 is accumulated in the refrigerant storage tank
25, and the refrigerant storage tank 25 is filled with liquid
refrigerant. The refrigerant just before entering the refrigerant
storage tank 25 includes a gas component produced when the
refrigerant is depressurized in the first expansion mechanism 24,
but after entering the refrigerant storage tank 25, the refrigerant
is divided into a liquid component and a gas component, the liquid
refrigerant is stored in the lower side, and the gas refrigerant is
stored in the upper side. At this time, because the flow rate
adjustment mechanism 30a of the bypass tube 30 is controlled to an
open state, the gas refrigerant in the refrigerant storage tank 25
passes through the bypass tube 30 and heads to the intake tube 31
of the compressor 21. The liquid refrigerant in the refrigerant
storage tank 25 is sent through the liquid-side shutoff valve 27
and the liquid refrigerant communication tube 5 to the indoor heat
exchanger 41 after being depressurized to a low pressure by the
second expansion mechanism 26 functioning as a downstream-side
expansion mechanism.
[0091] The low-pressure refrigerant sent to the indoor heat
exchanger 41 undergoes heat exchange with indoor air and evaporates
in the indoor heat exchanger 41. The indoor air is thereby cooled.
At this time, the refrigerant flowing into the indoor heat
exchanger 41 is reduced by the gas-liquid separating process in the
refrigerant storage tank 25, as well as the process of drawing the
gas-liquid separated gas refrigerant through the bypass tube 30
into the compressor 21. Therefore, the flow rate of refrigerant
flowing through the indoor heat exchanger 41 decreases, pressure
loss can be reduced proportionately, and the depressurization loss
in the refrigeration cycle can therefore be reduced.
[0092] The low-pressure refrigerant evaporated in the indoor heat
exchanger 41 is drawn through the gas refrigerant communication
tube 6, the gas-side shutoff valve 28, and the switching mechanism
22 back into the compressor 21.
[0093] (3) Characteristics of Air-Conditioning Apparatus
[0094] The air-conditioning apparatus 1 of the present embodiment
has the following characteristics.
[0095] <A>
[0096] In the air-conditioning apparatus 1, as described above, the
indoor heat exchanger 41 is a cross-fin type heat exchanger, the
outdoor heat exchanger 23 is a stacked heat exchanger, and the
capacity of the outdoor heat exchanger 23 is 100% or less of the
capacity of the indoor heat exchanger 41.
[0097] Therefore, in the air-conditioning apparatus 1, excess
refrigerant is produced during the air-cooling operation as a
cooling operation. When too much of this excess refrigerant spreads
from the indoor heat exchanger 41 having a gas-phase portion to
portions as far as the intake side of the compressor 21, there is a
risk that refrigerant control will be hindered.
[0098] In view of this, in the air-conditioning apparatus 1, the
refrigerant storage tank 25 for storing refrigerant depressurized
by an upstream-side expansion mechanism is provided between one of
the first expansion mechanism 24 and the second expansion mechanism
26 as an upstream-side expansion mechanism, and the other of the
first expansion mechanism 24 and the second expansion mechanism 26
as a downstream-side expansion mechanism, as described above. In
the air-conditioning apparatus 1, the excess refrigerant that can
no longer be accommodated in the outdoor heat exchanger 23 during
the air-cooling operation is then accommodated in the refrigerant
storage tank 25 positioned in the vicinity of the downstream side
of the outdoor heat exchanger 23.
[0099] It is thereby possible to prevent hindrances to refrigerant
control in the air-conditioning apparatus 1 because it is possible
to prevent too much refrigerant from spreading from the indoor heat
exchanger 41 having a gas-phase portion to portions as far as the
intake side of the compressor 21.
[0100] <B>
[0101] In the air-conditioning apparatus 1, a bypass tube 30 is
provided as described above. The bypass tube 30 is designed to lead
the gas component of the refrigerant accumulated in the refrigerant
storage tank 25 to either the compressor 21 or the intake tube 31
of the compressor 21.
[0102] In the air-conditioning apparatus 1, refrigerant
depressurized in one of the first expansion mechanism 24 and the
second expansion mechanism 26 as an upstream-side expansion
mechanism is separated info a liquid component and a gas component
in the refrigerant storage tank 25, and the gas component heads
toward the bypass tube 30.
[0103] The gas component, which does not contribute to evaporation,
thereby ceases to flow into the outdoor heat exchanger 23
functioning as an evaporator of refrigerant during the air-warming
operation in the air-conditioning apparatus 1, it is therefore
possible to proportionately reduce the flow rate of refrigerant
flowing through the outdoor heat exchanger 23 functioning as an
evaporator of refrigerant, and the depressurization loss in the
refrigeration cycle can be reduced.
[0104] <C>
[0105] When the operating frequency of the compressor 21 is high,
there is a risk that gas-liquid two-phase refrigerant from the
refrigerant storage tank 25 will pass through the bypass tube 30,
return to the compressor 21 or the intake tube 31 of the compressor
21, and be drawn into the compressor 21.
[0106] However, in the air-conditioning apparatus 1, because the
flow rate adjustment mechanism 30a is provided to the bypass tube
30, the liquid component of the gas-liquid two-phase refrigerant is
depressurized and evaporated.
[0107] It is thereby possible in the air-conditioning apparatus 1
to prevent the liquid component from returning to the compressor 21
or the intake tube 31 of the compressor 21.
[0108] <D>
[0109] During the air-warming operation in the air-conditioning
apparatus 1, refrigerant that has passed through the flow rate
adjustment mechanism 30a converges with refrigerant which has
evaporated in the indoor heat exchanger 41 and/or the outdoor heat
exchanger 23, and then heads to the compressor 21 or the intake
tube 31 of the compressor 21. At this time, in the case that the
flow rate adjustment mechanism 30a is an electric expansion valve,
the state of the refrigerant just before being drawn into the
compressor 21 can be adjusted more optimally by controlling the
valve opening degree. Moreover, because the flow rate of
refrigerant returning to the compressor 21 can be increased or
reduced by controlling the valve opening degree of the flow rate
adjustment mechanism 30a, the refrigerant circulation flow rate,
i.e. the flow rate of refrigerant flowing through the indoor heat
exchanger 41 can be controlled according to the refrigeration load
on the indoor heat exchanger 41 side.
[0110] (4) Modification 1
[0111] In the above embodiment, a container for storing refrigerant
is employed as the refrigerant storage tank 25, but refrigerant
storage is not limited as such, and a cyclone-type gas-liquid
separator such as the one shown in FIG. 5 may be employed, for
example.
[0112] The refrigerant storage tank 25 of the present modification
has primarily a cylindrical container 251, a first connecting tube
252, a second connecting tube 253, and a third connecting tube
254.
[0113] The first connecting tube 252 is linked in the tangential
direction of the circumferential side wall of the cylindrical
container 251, communicating the interior of the cylindrical
container 251 and the second expansion mechanism 26 or first
expansion mechanism 24 as a downstream-side expansion mechanism.
The second connecting tube 253 is linked to the bottom wall of the
cylindrical container 251, communicating the interior of the
cylindrical container 251 and the first expansion mechanism 24 or
second expansion mechanism 26 as an upstream-side expansion
mechanism. The third connecting tube 254 is linked to the top wall
of the cylindrical container 251, communicating the interior of the
cylindrical container 251 and the bypass tube 30.
[0114] Due to this configuration, intermediate-pressure refrigerant
flowing into the cylindrical container 251 through the first
connecting tube 252 flows so as to eddy along the internal
peripheral surface 251a of the circumferential side wall of the
cylindrical container 251, at which time the liquid refrigerant
adheres to the internal peripheral surface 251a, and the liquid
refrigerant and gas refrigerant are efficiently separated.
[0115] The liquid refrigerant falls due to gravity, accumulates in
the lower side, and flows out of the cylindrical container 251
through the second connecting tube 253. The gas refrigerant rises
while swirling, accumulates in the upper side, and flows out of the
cylindrical container 251 through the third connecting tube
254.
[0116] In the present modification, gas-liquid separation can be
efficiently performed because a cyclone-type gas-liquid separator
is employed as the refrigerant storage tank 25 as described above.
The refrigerant storage tank 25 composed of a gas-liquid separator
has both a refrigerant storage function of accumulating liquid
refrigerant and a function of separating the liquid component and
gas component, thereby contributing to simplifying the apparatus
configuration because there is no need to provide both a
refrigerant storage container and a gas-liquid separator.
[0117] (5) Modification 2
[0118] In the above embodiment and Modification 1, an example was
given in which the outdoor heat exchanger 23 is a stacked heat
exchanger having a plurality of flat tubes 231 and corrugated fins
232. In this outdoor heat exchanger 23, the plurality of flat,
tubes 231 are arrayed so as to be superposed set apart by gaps, and
the corrugated fins 232 are enclosed between adjacent flat tubes
231.
[0119] However, the outdoor heat exchanger 23 is not limited to the
configurations in the above embodiment and Modification 1, and may
be a stacked heat exchanger having a plurality of flat tubes 231
arrayed so as to be superposed set apart by gaps, and fins 236 in
which notches 236a are formed, the flat tubes 231 being inserted
into the notches, as shown in FIGS. 6 and 7, for example.
[0120] The same operational effects as those of the above
embodiment and Modification 1 can be achieved in this case as
well.
[0121] (6) Modification 3
[0122] In the above embodiment and Modification 1, an example was
given in which the outdoor heat exchanger 23 is a stacked heat
exchanger having a plurality of flat tubes 231 and corrugated fins
232. In this outdoor heat exchanger 23, the plurality of flat tubes
231 are arrayed so as to be superposed set apart by gaps, and the
corrugated fins 232 are enclosed between adjacent flat tubes
231.
[0123] However, the outdoor heat exchanger 23 is not limited to the
configurations in the above embodiment and Modification 1, and may
have a configuration in which the flat tubes are molded into
serpentine shapes and the fins are enclosed between the mutually
adjacent surfaces of the flat tubes, for example.
[0124] The same operational effects as those of the above
embodiment and Modifications 1 and 2 can be achieved in this case
as well.
[0125] (7) Modification 4
[0126] In the above embodiment and Modifications 1 to 3, the
outdoor heat exchanger 23 is a stacked heat exchanger having a
plurality of flat tubes 231, corrugated fins 232, and/or fins 236
in which notches 236a are formed. In the case of a refrigeration
apparatus in which the outdoor heat exchanger 23 is cooled by water
during the air-cooling operation, for example, the outdoor heat
exchanger 23 and the indoor heat exchanger 41 may both be cross-fin
type heat exchangers, configured such that the diameter of the heat
transfer tubes in the outdoor heat exchanger 23 is less than the
diameter of the heat transfer tubes in the indoor heat exchanger
41.
[0127] The same operational effects as those of the above
embodiment and Modifications 1 to 3 can be achieved in this case as
well.
[0128] (8) Modification 5
[0129] In the above embodiment and Modifications 1 to 4, various
refrigerants can be used as the refrigerant sealed within the
refrigerant circuit 10, but R32, a type of HFC-based refrigerant,
could be used as one type thereof, for example.
[0130] However, when R32 is used as the refrigerant in the
refrigeration apparatus, refrigerator oil sealed with the
refrigerant in order to lubricate the compressor 21 tends to have
extremely low solubility in low-temperature conditions. Therefore,
at a low pressure in the refrigeration cycle, the solubility of the
refrigerator oil greatly decreases due to the decrease in
refrigerant temperature. During the air-cooling operation in the
refrigerant circuit 10, there is low pressure in the refrigeration
cycle in the circuit portion beginning after passing through the
second expansion mechanism 26 functioning as a downstream-side
expansion mechanism and leading through the indoor heat exchanger
41 up to intake in the compressor 21. During the air-warming
operation, there is low pressure in the refrigeration cycle in the
circuit portion beginning after passing through the first expansion
mechanism 24 functioning as a downstream-side expansion mechanism
and leading through the outdoor heat exchanger 23 up to intake in
the compressor 21. The refrigerator oil when R32 is used as the
refrigerant could be ether-based synthetic oil having any
compatibility with R32, mineral oil or alkyl benzene-based
synthetic oil having no compatibility with R32, or the like. With
ether-based synthetic oil, compatibility is lost when the
temperature decreases to about -5.degree. C., and with mineral oil
or alkyl benzene-based synthetic oil, there is no compatibility at
conditions of higher temperature than ether-based synthetic oil.
When R32 is used as the refrigerant in a conventional refrigeration
apparatus having a refrigerant storage tank on the intake side of
the compressor, for example, the refrigerant and the refrigerator
oil separate into two layers in the refrigerant storage tank which
has a low pressure in the refrigeration cycle, and the refrigerator
oil has difficulty returning to the compressor.
[0131] However, in the refrigeration apparatus 1 of the present
modification, because a refrigerant storage tank 25 is provided
between the first and second expansion mechanisms 24, 26 as an
upstream-side expansion mechanism and a downstream-side expansion
mechanism as indicated in the above embodiment and Modifications 1
to 4, two-layer separation is less likely to occur in the intake
side of the compressor 21 and refrigerator oil returns more readily
to the compressor 21, in comparison to cases in which the
refrigerant storage tank is provided to the intake side of the
compressor 21.
[0132] Thus, in the refrigeration apparatus 1 of the present
modification, due to the refrigerant storage tank 25 being provided
between the first and second expansion mechanisms 24, 26 as an
upstream-side expansion mechanism and a downstream-side expansion
mechanism, if is possible to resolve not only the problem of excess
refrigerant produced by the capacity of the outdoor heat exchanger
23 being equal to or less than the capacity of the indoor heat
exchanger 41, due to factors such as a stacked heat exchanger being
used as the outdoor heat exchanger 23, but also the problem of oil
returning to the compressor 21, caused by using R32 as the
refrigerant.
INDUSTRIAL APPLICABILITY
[0133] The present invention is widely applicable in refrigeration
apparatuses that can perform a cooling operation and a heating
operation.
REFERENCE SIGNS LIST
[0134] 1 Air-conditioning apparatus (refrigeration apparatus)
[0135] 21 Compressor [0136] 23 Outdoor heat exchanger [0137] 24, 26
Expansion mechanisms [0138] 25 Refrigerant storage tank [0139] 30
Bypass tube [0140] 30a Flow rate adjustment mechanism [0141] 41
Indoor heat exchanger
CITATION LIST
Patent Literature
[0142] <Patent Literature 1>
Japanese Laid-open Patent Application No. 6-143991
* * * * *