Technical Field
[0001] This invention relates to a refrigeration cycle apparatus including means for physically
cleaning a foreign substance with a refrigerant, when an extension pipe part of a
refrigeration cycle apparatus that used mineral oil, such as mineral oil used for
a CFC refrigerant or an HCFC refrigerant, as refrigerating machine oil, is reused
in a refrigeration cycle apparatus that uses another refrigerant for an HFC refrigerant
system or the like, the foreign substance being mainly mineral oil and a deteriorated
substance of the mineral oil remaining in the extension pipe part.
Background Art
[0002] A known conventional cleaning technique for an extension pipe is as follows. An air-conditioning
device and a use-side heat exchanger, which are connected with an existing pipe and
required to be replaced, are removed, and a cleaning device and a bypass pipe are
connected with the existing pipe. After the connection, a vacuum is created in the
entire refrigeration cycle, and R407C is appropriately filled. Then, a compressor
is operated. A high-temperature high-pressure gas refrigerant discharged from the
compressor first passes through an oil separator. In this phase, refrigerating machine
oil discharged from the compressor together with the gas refrigerant is separated
by the oil separator, and is returned to a suction side of the compressor. The high-temperature
high-pressure gas refrigerant then passes through a four-way valve, the gas is partly
cooled by a high-low pressure heat exchanger and becomes liquid, and the refrigerant
becomes a high-pressure two-phase gas-liquid refrigerant. The high-pressure two-phase
gas-liquid refrigerant passes through the existing pipe, the bypass pipe, and the
existing pipe, then the pressure of the refrigerant is reduced by a pressure reducing
device, and the refrigerant becomes a low-pressure two-phase gas-liquid refrigerant.
Then, the refrigerant is heated by the high-low pressure heat exchanger and becomes
low-pressure gas. Then, the gas passes through a separating device, at this time,
the mineral oil cleaned in the existing pipe is separated, and the mineral oil is
held in the separating device. The temperature of the low-pressure refrigerant gas
is decreased by a heat-source-side heat exchanger to prevent a discharge temperature
of the compressor from becoming too high, and the gas is sucked by the compressor
through the four-way valve and an accumulator (Patent Literature 1).
GB 2 411 712 A discloses an air conditioning apparatus according to the preamble of claim 1, including
a refrigeration cycle in which a plurality of mesh strainers is disposed within a
refrigerant circuit along which a compressor, a four-way valve, a condenser, a first
electric expansion valve, a fluid reservoir mechanism, a second electric expansion
valve, a fluid line, an evaporator, and a gas line. A drying filter for trapping foreign
matter is disposed between the second electric expansion valve and the fluid line,
to trap foreign matter remaining in the existing lines, such as dust from abrasion
in the compressor, and deteriorated oil. An activated charcoal filter, for trapping
organic acids, inorganic acids, and chlorine, is positioned in a bypass line. A capillary
unit is preferably positioned after the charcoal filter.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0004] With the conventional technique like Patent Literature 1, foreign-substance capturing
means that contributes to cleaning for a foreign substance such as mineral oil is
arranged at a low-pressure side of a cooling operation. Hence, performance has been
likely degraded due to a pressure loss.
MITSUBISHI ELECTRIC CORPORATION
139EP 0986
[0005] Also, a structure is markedly different from that of an air-conditioning apparatus
including a normal refrigeration cycle. Hence, standardization and optional provision
of the foreign-substance capturing means have been difficult. Also, heat exchange
is performed between main pipes. Hence, a heat exchanger at this portion has been
increased in size and cost. Therefore, it is an object of the invention to provide
a low cost foreign substance recovery refrigerant circuit which is compatible with
conventional refrigerant circuits and that can thus be easily added.
Solution to Problem
[0006] A refrigeration cycle apparatus according to a first invention of this invention
is a refrigeration cycle apparatus having the features of claim 1, including a main
refrigerant circuit, through which a refrigerant circulates through a compressor,
a heat-source-side heat exchanger, a first flow rate control device, and a use-side
heat exchanger. The refrigeration cycle apparatus includes a first gas-liquid separator;
and a foreign-substance recovery container that recovers a foreign substance contained
in the refrigerant. A foreign-substance recovery refrigerant circuit that connects
the first gas-liquid separator with the foreign-substance recovery container through
a first passage opening and closing device is arranged between a suction side of the
compressor and the use-side heat exchanger, in parallel with the main refrigerant
circuit.
[0007] A low-pressure-side pipe of a high-low pressure heat exchanger, a second gas-liquid
separator, and a second passage opening and closing device are connected in that order
between the first passage opening and closing device and the foreign-substance recovery
container. A position of the first gas-liquid separator is preferably higher than
a position of the second gas-liquid separator.
[0008] Also, if an accumulator is provided between the compressor and the use-side heat
exchanger, an entrance of the foreign-substance recovery refrigerant circuit is preferably
connected with an inlet of the accumulator, and an exit of the foreign-substance recovery
refrigerant circuit is preferably connected with an outlet of the accumulator.
Advantageous Effects of Invention
[0009] With the refrigeration cycle apparatus configured as described above, a difference
in refrigerant circuit configuration is small with respect to a configuration of a
refrigeration cycle without the foreign-substance recovery refrigerant circuit. Accordingly,
the foreign-substance recovery refrigerant circuit that can be easily added and that
is low in cost can be realized.
Brief Description of Drawings
[0010]
[Fig. 1] Fig. 1 is a refrigerant circuit diagram of a refrigeration cycle apparatus
according to Embodiment 1 of this invention.
[Fig. 2] Fig. 2 is a flow diagram of a refrigerant in a cooling operation state according
to Embodiment 1 of this invention.
[Fig. 3] Fig. 3 is a flow diagram of the refrigerant in a heating operation state
according to Embodiment 1 of this invention.
[Fig. 4] Fig. 4 is a flowchart of a cleaning control method for an extension pipe
according to Embodiment 1 of this invention.
[Fig. 5] Fig. 5 is a refrigerant circuit diagram of a refrigeration cycle apparatus
according to Embodiment 2 of this invention.
[Fig. 6] Fig. 6 is a configuration diagram showing an example of foreign-substance
capturing means according to Embodiment 1 of this invention. Description of Embodiments
Embodiment 1
[0011] Fig. 1 is a refrigerant circuit diagram of a refrigeration cycle apparatus (an air-conditioning
apparatus) according to Embodiment 1 of this invention. A main refrigerant circuit
of this air-conditioning apparatus includes, for example, a compressor 1; a four-way
valve 2 serving as a flow switching valve; heat-source-side heat exchangers 3A and
3B; first flow rate control devices 4A, 4B, and 4C that control flow rates of a refrigerant
in refrigerant circuits; use-side heat exchangers 5A, 5B, and 5C; and an accumulator
9. The accumulator 9 may be provided as required.
[0012] A series circuit of the first flow rate control device 4A and the use-side heat exchanger
5A, a series circuit of the first flow rate control device 4B and the use-side heat
exchanger 5B, and a series circuit of the first flow rate control device 4C and the
use-side heat exchanger 5C are respectively components of an indoor unit A, an indoor
unit B, and an indoor unit C, and are connected in parallel. The number of the indoor
units is not particularly limited.
[0013] Also, an oil recovery unit 23 is provided between the compressor 1 and the four-way
valve 2, and a first gas-liquid separator 20 is provided between the four-way valve
2 and the accumulator 9 (if the accumulator 9 is not provided, the compressor 1).
[0014] A double-pipe heat exchanger 7 is provided between the heat-source-side heat exchangers
3A and 3B, and the first flow rate control devices 4A, 4B, and 4C. The double-pipe
heat exchanger 7 includes a high-pressure-side pipe 7A and a low-pressure-side pipe
7B and serves as a high-low pressure heat exchanger. Also, a third flow rate control
device 27 and a fifth opening and closing valve 28 are provided between the double-pipe
heat exchanger 7 and the first flow rate control devices 4A, 4B, and 4C. The third
flow rate control device 27 controls a downstream pressure during a cooling operation.
Further, a sixth opening and closing valve 29 is provided between the use-side heat
exchangers 5A, 5B, and 5C, and the four-way valve 2.
[0015] It is assumed that a pipe that connects the fifth opening and closing valve 28 with
the first flow rate control devices 4A, 4B, and 4C is called liquid-side extension
pipe (E), and a pipe that connects the sixth opening and closing valve 29 with the
use-side heat exchangers 5A, 5B, and 5C is called gas-side extension pipe (F).
[0016] A refrigerant circulates in the main refrigerant circuit configured as described
above, in accordance with a direction of the four-way valve 2, the direction which
is switched depending on whether operation is the cooling operation or a heating operation.
[0017] In this air-conditioning apparatus, a first bypass is further provided, in which
a second flow rate control device 6, the low-pressure-side pipe 7B of the double-pipe
heat exchanger 7, a second gas-liquid separator 21, a second opening and closing valve
11 serving as a second passage opening and closing device, a foreign-substance recovery
container 8, and a first check valve 12 are connected in series. The first bypass
is divided from a pipe between the heat-source-side heat exchanger 3 and the third
flow rate control device 27, and is connected with a refrigerant pipe between the
compressor 1 and the accumulator 9 (if the accumulator 9 is not provided, the first
gas-liquid separator 20).
[0018] Also, a pipe between the accumulator 9 and the first gas-liquid separator 20 is connected
with the second gas-liquid separator 21 through a second bypass including a second
check valve 26.
[0019] Further, a pipe between the second flow rate control device 6 and the low-pressure-side
pipe 7B of the double-pipe heat exchanger 7 is connected with the first gas-liquid
separator 20 through a third bypass including a first opening and closing valve 10
serving as a first passage opening and closing device.
[0020] The first gas-liquid separator 20, the first opening and closing valve 10, the low-pressure-side
pipe 7B of the double-pipe heat exchanger 7, the second gas-liquid separator 21, the
second opening and closing valve 11, and the foreign-substance recovery container
8 form a foreign-substance recovery refrigerant circuit serving as foreign-substance
recovery means for recovering a foreign substance in the refrigerant.
[0021] The normal direction of the first check valve 12 is a direction toward the compressor
1, and the normal direction of the second check valve 26 is a direction toward the
accumulator 9.
[0022] Also, the first gas-liquid separator 20 causes a liquid phase to flow toward the
first opening and closing valve 10, and causes a gas phase to flow toward the accumulator
9.
[0023] Also, the second gas-liquid separator 21 causes a liquid phase to flow toward the
second opening and closing valve 11, and causes a gas phase to flow toward the second
check valve 26.
[0024] Also, first pressure detecting means 13 and second pressure detecting means 14 are
respectively connected at a discharge side and a suction side of the compressor 1.
[0025] In addition, third pressure detecting means 15 is connected with middle part of a
pipe that connects the third flow rate control device 27 with the fifth opening and
closing valve 28.
[0026] Further, first temperature detecting means 16 is provided at the discharge side of
the compressor 1, and second temperature detecting means 17 is provided at a pipe
between the low-pressure-side pipe 7B of the double-pipe heat exchanger 7 and the
second gas-liquid separator 21.
[0027] Third temperature detecting means 18A, 18B, and 18C are respectively connected between
the first flow rate control devices 4A, 4B, and 4C, and the corresponding use-side
heat exchangers 5A, 5B, and 5C.
[0028] Also, fourth temperature detecting means 19A, 19B, and 19C are respectively connected
between the use-side heat exchangers 5A, 5B, and 5C, and the gas-side extension pipe
(F), at the use-side heat exchanger sides.
[0029] Further, fifth temperature detecting means 22 is provided for detecting an outdoor
temperature.
[0030] Elements surrounded by a broken line in Fig. 1 represent components of an outdoor
unit (D).
[0031] Next, a flow of the refrigerant in the refrigerant circuit shown in Fig. 1 is described
with reference to Figs. 2 and 3. As shown in Fig. 2, in a normal cooling operation,
a refrigerant containing refrigerating machine oil is discharged from the compressor
1, the refrigerating machine oil is separated by the oil recovery unit 23, the refrigerant
passes through the four-way valve 2, and the refrigerant exchanges heat with the air
by the heat-source-side heat exchanger 3, so that the refrigerant is condensed and
liquefied. Then, the refrigerant is further cooled in the high-pressure-side pipe
7A of the double-pipe heat exchanger 7, the pressure of part of the cooled refrigerant
is adjusted by the third flow rate control device 27, then the refrigerant passes
through the fifth opening and closing valve 28 being open, and then the refrigerant
enters the first flow rate control devices 4A, 4B, and 4C of the indoor units through
the liquid-side extension pipe (E). The refrigerant with the pressure reduced by the
first flow rate control devices 4A, 4B, and 4C exchanges heat with the air in the
use-side heat exchangers 5A, 5B, and 5C, so that the refrigerant is evaporated and
gasified; the refrigerant passes through the liquid-side extension pipe (F), the sixth
opening and closing valve 29 being open, the four-way valve 2, the first gas-liquid
separator 20, and the accumulator 9; and the refrigerant is returned to the suction
side of the compressor 1.
[0032] In contrast, part of the refrigerant after the refrigerant passes through the high-pressure-side
pipe 7A of the double-pipe heat exchanger 7 is reduced in pressure by the second flow
rate control device 6; the refrigerant exchanges heat in the low-pressure-side pipe
7B of the double-pipe heat exchanger with the high-pressure-side pipe 7A, so that
the refrigerant is evaporated; the refrigerant passes through the second gas-liquid
separator 21 and the second check valve 26; and the refrigerant flows into the pipe
that connects the first gas-liquid separator 20 with the accumulator 9. In normal
cooling operation, the first opening and closing valve 10 and the second opening and
closing valve 11 are closed, and the refrigerant does not flow from the first gas-liquid
separator 20 to the first opening and closing valve 10, or from the second gas-liquid
separator 21 to the second opening and closing valve 11.
[0033] The first flow rate control devices 4A, 4B, and 4C control respective differences
of detected temperature between the fourth temperature detecting devices 19A, 19B,
and 19C and the third temperature detecting devices 18A, 18B, and 18C to be a constant
numerical value, for example, "2." The second flow rate control device 6 adjusts a
difference of detected temperature between the second temperature detecting device
17 and a saturation temperature of detected pressure of the second pressure detecting
device 14 to be, for example, "5." The third flow rate control device 27 adjusts a
numerical value of the third pressure detecting device 15 to be, for example, "3.0
MPa." The control value provided by the third pressure detecting device 15 is a value
set to be equal to or smaller than an allowable value for a pipe.
[0034] In the heating operation, mineral-oil recovery operation is not performed, but only
a normal heating operation is performed. As shown in Fig. 3, the refrigerant containing
the refrigerating machine oil is discharged from the compressor 1; the refrigerating
machine oil is separated by the oil recovery unit 23, the refrigerant passes through
the four-way valve 2, the sixth opening and closing valve 29 being open, and the liquid-side
extension pipe (F); then the refrigerant exchanges heat with the air in the use-side
heat exchangers 5A, 5B, and 5C, so that the refrigerant is condensed and liquefied;
and the refrigerant is reduced in pressure by the first flow rate control devices
4A, 4B, and 4C, so that the refrigerant becomes a two-phase state. The refrigerant
in the two-phase state passes through the gas-side extension pipe (E), the fifth opening
and closing valve 28 being open, the third flow rate control device 27 being full
open, and the pipe 7A of the double-pipe heat exchanger; the refrigerant exchanges
heat with the air by the heat-source-side heat exchanger 3, so that the refrigerant
is evaporated and gasified; and then the refrigerant is returned to the suction side
of the compressor 1 through the four-way valve 2. Since the second flow rate control
device 6 is full open, the refrigerant does not flow to the pipe 7B of the double-pipe
heat exchanger. Also, if the first flow rate control devices 4A, 4B, and 4C are controlled,
subcooling at exit portions of the use-side heat exchangers 5A, 5B, and 5C can be
controlled. The subcooling at the exit portions is indicated by values, each of which
is obtained by subtracting corresponding one of detected temperatures by the second
temperature detecting means 18A, 18B, and 18C from a saturation temperature of a detected
pressure by the first pressure detecting means 13.
[0035] Described next is a flow of the refrigerant during a foreign-substance recovery operation
for recovering a foreign substance, which mainly contains the mineral oil and the
deteriorated substance of the mineral oil remaining in the gas-side extension pipe
(E) and the liquid-side extension pipe (F), in view of a difference with respect to
the normal cooling operation. If only an extension pipe portion (in this case, the
liquid extension pipe (E) and the gas extension pipe (F)) is reused, the portion being
included in a refrigeration system that uses mineral oil, such as mineral oil used
for a CFC refrigerant or an HCFC refrigerant, as refrigerating machine oil, and the
refrigeration system is changed to a refrigeration system that uses another refrigerant
such as an HFC refrigerant (in this case, the outdoor unit D and the indoor units
A, B, and C are renewed for the HFC refrigerant), this foreign-substance recovery
operation is performed to remove the foreign substance mainly including the mineral
oil and the deteriorated substance of the mineral oil, which adversely affect on the
refrigeration cycle with the HFC refrigerant.
[0036] In this operation, the first opening and closing valve 10 and the second opening
and closing valve 11 that are closed in the normal cooling operation are opened, and
the second flow rate control device 6 is closed. Accordingly, the refrigerant does
not flow to the second flow rate control device 6 as compared with the flow during
the normal cooling operation. Instead of this, a liquid phase separated by the first
gas-liquid separator 20 enters the pipe 7B of the double-pipe heat exchanger through
the first opening and closing valve 10, the liquid phase is heated and evaporated
in the pipe 7B, the gas and liquid are separated by the second gas-liquid separator
21, the refrigerant of a liquid phase or two phases flows to the foreign-substance
recovery container 8 through the second opening and closing valve 11, and only the
gas refrigerant is returned to the suction side of the compressor 1 through the first
check valve 12.
[0037] As shown in Fig. 6, a primary portion of the foreign-substance capturing means may
be configured of a simple structure (the second gas-liquid separator 21, the second
opening and closing valve 11, and the foreign-substance recovery container 8), and
may be created with a low cost.
[0038] Described next is movement of the refrigerant during the foreign-substance recovery
operation and mineral oil that initially remains in a pipe extending from the third
flow rate control device 27 to the four-way valve 2 through the first flow rate control
devices 4A, 4B, and 4C.
[0039] In the foreign-substance recovery operation, the indoor units 4A to 4C are partly
operated, for example, only the use-side heat exchanger 5A is operated. The first
flow rate control device 4A is full open, the first flow rate control devices 4B and
4C are full closed, the second flow rate control device 6 is full closed, and third
flow rate control device 27 is operated similarly to normal cooling control. In this
case, since the refrigerant output from the third flow rate control device 27 is not
completely evaporated by the use-side heat exchanger 5A, the refrigerant becomes an
annular two-phase refrigerant. The refrigerant reaches the first gas-liquid separator
20 through the four-way valve 2 while the refrigerant removes and flushes the mineral
oil adhering to the pipe. From the first gas-liquid separator 20, the removed foreign
substance and the liquid phase enter the pipe 7B of the double-pipe heat exchanger
through the first opening and closing valve 10, the refrigerant is slightly evaporated
in the pipe 7B, then the refrigerant enters the second gas-liquid separator 21, and
the liquid phase and the mineral oil remaining in the second gas-liquid separator
21 are recovered by the foreign-material recovery container 8. In this case, a single
indoor unit is operated every constant time. After all indoor units are similarly
individually operated, the normal cooling operation is performed for a short time,
for example, 20 seconds. Hence, the mineral oil finally remaining in the pipe 7B of
the double-pipe heat exchanger is recovered in the foreign-substance recovery container
8, then the compressor 1 is stopped, and then the first opening and closing valve
10 and the second opening and closing valve 11 are closed.
[0040] The first gas-liquid separator 20 is arranged at a higher position than the position
of the second gas-liquid separator 21 so that the refrigerant flows from the first
gas-liquid separator 20 to the second gas-liquid separator 21. Accordingly, the foreign
substance can be further reliably recovered in the foreign-substance recovery container
8.
[0041] Also, the operation capacity of the indoor units 4A and 4B is determined to be an
annular two-phase flow so that the mineral oil in the pipe can be recovered.
[0042] Also, to prevent the refrigerant in the path located downstream of the third flow
rate control device 27 from flowing with difficulty in the form of annular two-phase
flow and from being evaporated with difficulty in the low-pressure-side pipe 7B of
the double-pipe heat exchanger 7 because the outside air is lowered, if the detected
temperature of the fifth temperature detecting means 22 is 10 degrees C or lower,
a third opening and closing valve 24 and a fourth opening and closing valve 25 are
closed, so that the high pressure is increased. If the detected temperature of the
fifth temperature detecting means 22 exceeds, for example, 10 degrees C, the third
opening and closing valve 24 and the fourth opening and closing valve 25 are opened.
[0043] Also, to prevent the liquid refrigerant to be excessively increased in the foreign-substance
recovery container 8, in the foreign-substance recovery operation, the opening degree
of each of the flow-rate control devices 4A, 4B, and 4C of the indoor units being
full open may be periodically alternately changed between the full open state and
a normal operation opening degree.
[0044] Fig. 4 explains the flow of the foreign-substance recovery operation with a flowchart.
Description is given below with reference to the flow in Fig. 4. After a replacement
work for a heat source device or an indoor unit, the foreign-substance recovery operation
is started (S1).
[0045] Then, the first opening and closing valve 10 and the second opening and closing valve
11 are opened (S2), and an indoor unit to be operated is determined (S3).
[0046] A constant-time operation is performed for each determined indoor unit (S4 to S7),
and then, the normal cooling operation is performed for about 20 seconds (S8).
[0047] Then, the foreign-substance recovery operation is ended, and the compressor 1 is
stopped (S9, S10). Then, the first opening and closing valve 10 and the second opening
and closing valve 11 are closed (S11).
Embodiment 2
[0048] Fig. 5 is a refrigerant circuit diagram of a refrigeration cycle apparatus according
to Embodiment 2 of this invention. As shown in Fig. 5, the liquid refrigerant separated
from the first gas-liquid separator 20 and the recovered foreign-substance (the mineral
oil etc.) may not pass through the double-pipe heat exchanger 7, but may directly
flow into the foreign-substance recovery container 8. In this case, the first gas-liquid
separator 20, the first opening and closing valve 10, and the foreign-substance recovery
container 8 form a foreign-substance recovery refrigerant circuit.
[0049] However, in this case, the size of the foreign-substance recovery container 8 is
preferably selected so as to allow the liquid refrigerant to be recovered therein.
Alternatively, the refrigerant recovery amount of the foreign-substance recovery container
8 is preferably restricted by alternately periodically changing the opening degree
of the flow rate control devices 4A, 4B, and 4C, the opening degree of which has been
full open during the foreign-substance recovery operation, between the full open and
the normal operation opening degree.
[0050] In any of the above-described embodiments, the accumulator 9 is provided between
the compressor 1 and the use-side heat exchangers 4A, 4B, and 4C. In this case, if
the entrance side of the foreign-substance recovery refrigerant circuit is connected
with the inlet side of the accumulator 9 and if the exit side of the foreign-substance
recovery refrigerant circuit is connected with the outlet side of the accumulator
9, the foreign substance can be further reliably recovered in the foreign-substance
recovery container 8.
Reference Signs List
[0051]
1: compressor, 2: four-way valve, 3A, 3B: heat-source-side heat exchanger, 4A, 4B,
4C: first flow rate control device (first expansion device), 5A, 5B, 5C: use-side
heat exchanger, 6: second flow rate control device (second expansion device), 7: double-pipe
heat exchanger (high-low pressure heat exchanger), 8: foreign-substance recovery container,
9: accumulator, 10: first opening and closing valve, 11: second opening and closing
valve, 12: first check valve, 13: first pressure detecting means, 14: second pressure
detecting means, 15: third pressure detecting means, 16: first temperature detecting
means, 17: second temperature detecting means, 18A, 18B, 18C: third temperature detecting
means, 19A, 19B, 19C: fourth temperature detecting means, 20: first gas-liquid separator,
21: second gas-liquid separator, 22: fifth temperature detecting means, 23: oil recovery
unit, 24: third opening and closing valve, 25: fourth opening and closing valve, 26:
second check valve, 27: third flow rate control device (third expansion device), 28:
fifth opening and closing valve, 29: sixth opening and closing valve, A: indoor unit
A, B: indoor unit B, C: indoor unit C, D: outdoor unit, E: liquid-side extension pipe,
F: gas-side extension pipe