U.S. patent application number 11/719775 was filed with the patent office on 2009-06-11 for air conditioner.
This patent application is currently assigned to MITSUBISHI DENKI KABUSHIKI KAISHA. Invention is credited to Toshihiko Enomoto, Tomohiko Kasai, Toshiyuki Nakamura, Jiro Okajima, Takashi Okazaki, Kunio Tojo, Shinichi Wakamoto.
Application Number | 20090145151 11/719775 |
Document ID | / |
Family ID | 36497883 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090145151 |
Kind Code |
A1 |
Wakamoto; Shinichi ; et
al. |
June 11, 2009 |
AIR CONDITIONER
Abstract
An air conditioner including an outdoor unit, indoor units, and
a relay device for connection between the outdoor unit and each of
the indoor units. The outdoor unit includes an outdoor heat
exchanger, a compressor for pressurizing a refrigerant of or
including carbon dioxide, and a first switching member for
switching flow direction of the refrigerant through the outdoor
heat exchanger. Each of the indoor units includes an indoor heat
exchanger and first flow controller in fluid communication between
first and second pipe connection ports. The relay device includes
second switching members, each of the second switching members
selectively connecting the first pipe connection port of a
respective indoor unit with the first or second connection end of
the outdoor unit.
Inventors: |
Wakamoto; Shinichi; (Tokyo,
JP) ; Kasai; Tomohiko; (Tokyo, JP) ; Okajima;
Jiro; (Tokyo, JP) ; Nakamura; Toshiyuki;
(Tokyo, JP) ; Tojo; Kunio; (Tokyo, JP) ;
Okazaki; Takashi; (Tokyo, JP) ; Enomoto;
Toshihiko; (Tokyo, JP) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW, SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
MITSUBISHI DENKI KABUSHIKI
KAISHA
Tokyo
JP
|
Family ID: |
36497883 |
Appl. No.: |
11/719775 |
Filed: |
November 1, 2005 |
PCT Filed: |
November 1, 2005 |
PCT NO: |
PCT/JP2005/020109 |
371 Date: |
July 9, 2007 |
Current U.S.
Class: |
62/259.1 ;
62/498 |
Current CPC
Class: |
F25B 9/008 20130101;
F25B 2313/0272 20130101; F25B 2313/02741 20130101; F25B 2313/006
20130101; F25B 2313/0231 20130101; F25B 2309/061 20130101; F25B
2400/04 20130101; F25B 13/00 20130101; F25B 2400/23 20130101; F25B
2313/0233 20130101 |
Class at
Publication: |
62/259.1 ;
62/498 |
International
Class: |
F25D 23/00 20060101
F25D023/00; F25B 1/00 20060101 F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 2004 |
JP |
2004-340889 |
Claims
1. An air conditioner, comprising: an outdoor unit including an
outdoor heat exchanger, a compressor for pressurizing a refrigerant
of carbon dioxide or a composite having carbon dioxide as a main
ingredient, and a first switching member for switching flow
direction of the refrigerant through the outdoor heat exchanger,
the outdoor heat exchanger, the compressor, and the first switching
member being in fluid communication between first and second
connection ends; a plurality of indoor units, each of the indoor
units including an indoor heat exchanger and a first flow
controller which are in fluid communication between first and
second pipe connection ports; and a relay device including a
plurality of second switching members, each of the second switching
members selectively connecting the first pipe connection port of a
respective indoor unit with either one of the first and second
connection ends of the outdoor unit, a first bypass pipe for
connection between the second connection end of the outdoor unit
and each of the second pipe connection ports of the indoor units,
and a second flow controller intervening in the first bypass pipe,
wherein when operated in a principally cooling mode, the
refrigerants air through t least one of the indoor heat exchangers
while remaining in a super critical state, without
condensation.
2. The air conditioner according to claim 1, wherein the compressor
has a refrigerant delivery port and a refrigerant suction port; and
the first switching member switches in accordance with operation
modes of the air conditioner between first and second conditions,
the first condition allowing connection of the refrigerant delivery
port to a first end of the outdoor heat exchanger and connection of
the refrigerant suction port to the first connection end, the
second condition allowing connection of the refrigerant delivery
port to the first connection end and connection of the refrigerant
suction port to the first end of the outdoor heat exchanger.
3. (canceled)
4. The air conditioner according to claim 2, further comprising: a
flow-path selector for guiding the refrigerant from the outdoor
heat exchanger to the second connection end and guiding the
refrigerant from the first connection end to the refrigerant
suction port when the first switching member switches to the first
condition, and for guiding the refrigerant from the refrigerant
delivery port to the second connection end and guiding the
refrigerant from the first connection end to the outdoor heat
exchanger when the first switching member switches to the second
condition; a second bypass pipe for fluid communication between the
first connection end of the outdoor unit and the first bypass pipe;
and a third flow controller intervening in the second bypass
pipe.
5. The air conditioner according to claim 4, wherein the flow-path
selector includes a first check valve intervening in a first path
between the first connection end and the compressor, a second check
valve intervening in a second path between the second connection
end and the outdoor heat exchanger, a third check valve intervening
in a third path between the first connection end and the outdoor
heat exchanger, and a fourth check valve intervening in a fourth
path between the second connection end and the compressor.
6. The air conditioner according to claim 4, including first and
second inter-unit pipes wherein the second switching member
connects to the first and second connection ends through the first
and second inter-unit pipes, respectively; and the first inter-unit
pipe has a pipe wall thickness thinner than that of the second
inter-unit pipe.
7. The air conditioner according to claim 1, wherein the first
switching member and each of the second switching members are
operable independently of other switching members.
8. The air conditioner according to claim 1, wherein the first
switching member includes a four-way switching valve.
9. The air conditioner according to claim 1, wherein each of the
second switching members includes a three-way switching valve
connected to the first and second connection ends of the outdoor
unit and the first pipe connection port of a respective indoor
unit.
10. The air conditioner according to claim 1, wherein each of the
second switching members includes a first two-way switching valve
connected to the first connection end of the outdoor unit and the
first pipe connection port of a respective indoor unit, and a
second two-way switching valve connected to the second connection
end of the outdoor unit and the first pipe connection port of a
respective indoor unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1) Technical Field of the Invention
[0002] The present invention generally relates to an air
conditioner applying a refrigeration cycle. In particular, the
present invention relates to a multi-split type air conditioner
including an outdoor unit and a plurality of indoor units,
performing in operation modes where all of the rooms are cooled and
heated, and in other operation modes where one of the rooms is
cooled while another one of the rooms is heated,
simultaneously.
[0003] 2) Description of Related Arts
[0004] Patent Document 1 discloses a multi-split type air
conditioner, which includes an outdoor unit having a compressor and
an outdoor heat exchanger, a plurality of indoor units, each having
an indoor heat exchanger, and a relay device for connection between
the outdoor unit and the indoor units, The multi-split type air
conditioner performs in the cooling and heating operation modes
cooling and heating all of the rooms, respectively. Also, it
performs in other operation modes cooling one of the rooms while
heating another one of the rooms simultaneously, which are referred
to as a principally-cooling operation mode where cooling operation
capacity is greater than heating operation capacity, and as a
principally-heating operation mode where heating operation capacity
is greater than cooling operation capacity.
[0005] In the principally-cooling operation mode, the conventional
air conditioner requires a vapor-liquid separation device for
separating vapor refrigerant and liquid refrigerant from the
refrigerant in a vapor-liquid mixed state generated by the outdoor
heat exchanger of the outdoor unit. A first bypass pipe has one end
connected to a liquid-phase outlet of the vapor-liquid separation
device and a plurality of other split ends, each of which connects
to a flow control device of the indoor unit. The flow control
device of the indoor unit in the room to be cooled decompresses the
high-pressurized liquid refrigerant for changing to the two-phase
vapor-liquid refrigerant of low temperature and low pressure, which
is supplied to the indoor heat exchanger. On the other hand, the
vapor refrigerant output from the vapor-liquid separation device is
supplied to the indoor unit of the room to be heated.
[0006] Patent Document 1: JP 9-042804, A
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0007] Since the liquid refrigerant output from the vapor-liquid
separation device is saturated liquid, unless it is overcooled, it
may somehow be decompressed in a way up to the flow control device
of the indoor unit so as to change its phase to the two-phase
vapor-liquid phase, thereby causing noise and pressure pulsation in
the flow control device. To suppress the problem, i.e., to overcool
the saturated liquid refrigerant, a second bypass pipe is arranged
adjacent and connected to the first bypass pipe, and another flow
control device for controlling the flow through the second bypass
pipe, which decompresses a portion of the liquid refrigerant output
from the vapor-liquid separation device to generate the two-phase
vapor-liquid refrigerant of low temperature and low pressure,
thereby overcooling the liquid refrigerant output from the
vapor-liquid separation device with the vapor-liquid is refrigerant
through the second bypass pipe. Also, in the vapor-liquid
separation device, another flow control device intervenes in the
first bypass pipe for controlling flow amount of the liquid
refrigerant output from the vapor-liquid separation device for
preventing the liquid refrigerant from being mixed in the vapor
refrigerant.
[0008] As above, the relay device of the conventional air
conditioner requires a lot of components. Also, due to too many
components, it is difficult to control the cooling and heating
capacity of the indoor heat exchangers. The above-described air
conditioner uses a fluorocarbon-based refrigerant having high score
of the global warming potential that is an index indicating the
degree how the greenhouse effect gas brings the global warming, as
a basis (=1) for carbon dioxide.
[0009] Therefore, one of the aspects of the present invention is to
provide a multi-split type air conditioner using the refrigerant of
carbon dioxide, which substantially reduces the number of
components of the relay device and improves controllability of the
cooling and heating features of the indoor heat exchangers.
Means for Solving the Problems
[0010] In order to achieve the above-described objects, an air
conditioner of one of the aspects according to the present
invention is to provide an air conditioner including an outdoor
unit, a plurality of indoor units, and a relay device for
connection between the outdoor unit and each of the indoor units.
The outdoor unit includes an outdoor heat exchanger, a compressor
for pressurizing a refrigerant of carbon dioxide or a composite
having main ingredient of carbon dioxide, and a first switching
member for switching a flow direction of the refrigerant through
the outdoor heat exchanger, which are in fluid communication
between first and second connection ends. Each of the indoor units
includes an indoor heat exchanger and a first flow controller which
are in fluid communication between first and second pipe connection
ports. The relay device includes a plurality of second switching
members, each of which the second switching members selectively
connects the first pipe connection port of the respective indoor
unit with the first or second connection end of the outdoor unit.
The relay device also includes a first bypass pipe for connection
between the second connection end of the outdoor unit and each of
the second pipe connection ports of the indoor units, and a second
flow controller intervening in the first bypass pipe.
ADVANTAGE OF THE INVENTION
[0011] In the principally cooling operation mode of the present
invention, the refrigerant flows through the refrigerant delivery
port of the compressor, the first switching member, the outdoor
heat exchanger, and the second connection end into the indoor unit
in the room to be heated, in which the refrigerant heats the air in
the indoor heat exchanger. After that, the refrigerant flows into
the indoor units in the rooms to be cooled, in which after the
refrigerant is decompressed when passing through the first flow
controller for cooling the air in the indoor heat exchangers of the
indoor units, following to the first connection end. The
refrigerant of carbon dioxide or a composite having main ingredient
of carbon dioxide remains in a supercritical state while flowing
from the refrigerant delivery port of the compressor prior to the
indoor heat exchangers of the indoor units. Therefore, the noise
and the pressure pulsation which might be generated at the first
flow controller can be suppressed or avoided. Thus, according to
the present invention, since the refrigerant is kept in the
supercritical state, unlike the conventional air conditioner, the
vapor-liquid separation device 40 and associated components can be
eliminated, which substantially reduce the number of the components
of the relay device. Also, the controllability of the indoor heat
exchanger for heating and cooling the rooms can fairly be improved
due to the fewer components.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a flow circuit of a refrigerant adapted in an air
conditioner of the first embodiment of the present invention.
[0013] FIG. 2 is the flow circuit similar to FIG. 1, indicating the
flow circulation of the refrigerant in a cooling operation
mode.
[0014] FIG. 3 is the flow circuit similar to FIG. 1, indicating the
flow circulation of the refrigerant in a heating operation
mode.
[0015] FIG. 4 is the flow circuit similar to FIG. 1, indicating the
flow circulation of the refrigerant in a principally-cooling
operation mode.
[0016] FIG. 5 is the flow circuit similar to FIG. 1, indicating the
flow circulation of the refrigerant in a principally-heating
operation mode.
[0017] FIG. 6 is a p-h diagram (pressure-enthalpy diagram) showing
transition of the refrigerant illustrated in FIG. 2.
[0018] FIG. 7 is a p-h diagram showing transition of the
refrigerant illustrated in FIG. 3.
[0019] FIG. 8 is a p-h diagram showing transition of the
refrigerant illustrated in FIG. 4.
[0020] FIG. 9 is a p-h diagram showing transition of the
refrigerant illustrated in FIG. 5.
[0021] FIG. 10 is a flow circuit of a refrigerant adapted in
another air conditioner, as an example for comparison with one of
the present invention.
[0022] FIG. 11 is a flow circuit of a refrigerant adapted in an air
conditioner of the second embodiment of the present invention.
[0023] FIG. 12 is the flow circuit similar to FIG. 11, illustrating
modification of the second embodiment.
DESCRIPTION OF THE REFERENCE NUMERALS
[0024] 2: air conditioner
[0025] 4: outdoor unit
[0026] 6P-6R: indoor unit
[0027] 8: relay device
[0028] 10: compressor
[0029] 10a: refrigerant delivery port
[0030] 10b: refrigerant suction port
[0031] 12: heat exchanger of an outdoor unit
[0032] 16: first switching member (four-way switching valve)
[0033] 18a, 18b: first and second inter-unit pipe
[0034] 20a, 20b: first and second connection end
[0035] 26a, 26b: first and second pipe connection port
[0036] 28: heat exchanger of an indoor unit
[0037] 32P-32R: first flow controller (flow control valve)
[0038] 34: first bypass pipe
[0039] 36: second flow controller (flow control valve)
[0040] 52: flow-path selector
[0041] 66: second bypass pipe
[0042] 68: third flow controller (flow control valve)
BEST MODE FOR CARRYING OUT THE INVENTION
[0043] Referring to the attached drawings, the details of
embodiments according to the present invention will be described
hereinafter.
EMBODIMENT 1
[0044] FIG. 1 illustrates the first embodiment of an air
conditioner according to the present invention. The air conditioner
2 uses carbon dioxide as a refrigerant, and includes, in general,
an outdoor unit 4, a plurality of indoor units 6, and a relay
device 8 for connection between the outdoor unit 4 and the indoor
units 6. While there are shown three of the indoor units 6 (i.e.,
6P, 6Q, 6R) in the present embodiment, the present invention cannot
be limited by the number of the indoor units 6, as long as the air
conditioner has more than two of the indoor units.
[0045] The air conditioner 2 performs in a cooling operation mode
in which each of the rooms having the respective indoor unit is to
be cooled, and in a heating operation mode in which each of the
rooms is to be heated. Also, it performs in another two modes where
one of the rooms is cooled while another one of the rooms is
heated, simultaneously (i.e., principally-cooling and
principally-heating operation modes).
[0046] The indoor unit 4 includes a compressor 10 for compressing
the refrigerant, a heat exchanger (outdoor heat exchanger) 12, and
a first switching member 16 such as a four-way switching valve, all
of which are in fluid communication between first and second
connection end 20a, 20b. In particular, the compressor 10 has a
refrigerant delivery port 10a and a refrigerant suction port 10b
connected to the first switching member 16 via the pipes 14a, 14b,
respectively. The first switching member 16 is also connected via
the pipe 14d to the first connection end 20a which is in turn
connected to a pipe 18a of the relay device 8. Further, the heat
exchanger 12 has one end 12a connected to the first switching
member 16 via the pipe 14c and the other end connected via the pipe
14e to a second connection end 20b which is in turn connected to
another pipe 18b of the relay device 8. As above, the pipes 18a,
18b are referred to as inter-unit pipes for connection between the
outdoor unit 4 and the indoor units 6P-6R.
[0047] The switching member 16 is designed to switch a flow
direction of the refrigerator through the heat exchanger 12 between
first and second flow conditions in accordance with the operation
modes. In the first flow condition as illustrated in FIG. 2, the
first connection end 20a is connected to the refrigerant suction
port 10b of the compressor 10 via the pipes 14d, 14b, and the
refrigerant delivery port 10a of the compressor 10 is connected to
one end 12a of the heat exchanger 12 via the pipes 14a, 14c, in
which the refrigerant flows from one end 12a to the other end 12b
of the heat exchanger 12. i.e., from the first connection end 20a
to the second connection end 20b. In the second flow condition as
illustrated in FIG. 3, one end 12a of the heat exchanger 12 is
connected to the refrigerant suction port 10b of the compressor 10
via the pipes 14c, 14b, and the refrigerant delivery port 10a of
the compressor 10 is connected to the first connection end 20a via
the pipes 14a, 14d, in which the refrigerant flows from the other
end 12b to one end 12a of the heat exchanger 12, i.e., from the
second connection end 20b to the first connection end 20a.
[0048] A relay device 8 includes a plurality of three-way switching
valves (second switching member) 22, e.g., three of the switching
valves 22P, 22Q, 22R in the present embodiment, each of which has
three of connection ports 24a, 24b, 24c. One inter-unit pipe 18a is
split and connected to the connection ports 24a of the switching
valves 22P, 22Q, 22R, and the other inter-unit pipe 18b is also
split and connected to the connection ports 24b of the switching
valves 22P, 22Q, 22R. Also, each of the connection ports 24c of the
switching valves 22P, 22Q, 22R is connected to the first pipe
connection port 26a of the respective indoor unit 6.
[0049] Each of the indoor units 6 includes another heat exchanger
(indoor heat exchanger) 28 and a flow control valve (first flow
controller) 32, which are in fluid communication between first and
second pipe connection ports 26a, 26b. In particular, the heat
exchanger 28 has one end connected via a pipe to the first pipe
connection port 26a, and the other end connected via a pipe 30 to
the second pipe connection port 26b which is in turn connected to a
bypass pipe of the relay member 8. Also, the flow control valves 32
(32P, 32Q, 32R) intervene in the pipe 30 for controlling the flow
of the refrigerant therethrough.
[0050] As above, the relay device includes the first bypass pipe 30
having one end connected to the inter-unit pipe 18b and the other
end split and connected to each of the second pipe connection ports
26b (and the flow control valves 32). Also, a second flow control
valve 36 intervenes in the bypass pipe 30 for controlling the flow
of refrigerant through the bypass pipe 30.
[0051] Next, the operation of the air conditioner 2 so structured
will be described herein, with reference to FIGS. 2-5 illustrating
the flow of the refrigerant and FIGS. 6-9 of the p-h diagram
showing the relationship between the pressure and the enthalpy of
the refrigerant. In FIGS. 2-5, the thick lines indicate pipes
through which the refrigerant is running and the bracket indexes
[i] (i=1, 2, . . . ) shows positions where the phases of the
refrigerant are illustrated by plotting the points with the bracket
indexes [i] on the diagrams in FIGS. 6-9.
<<Cooling Operation Mode (FIGS. 2 and 6)>>
[0052] When all of the indoor units 6P-6R perform the cooling
operation, the switching member 16 switches to the first flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with one end 12a of the heat exchanger 12 and by
connecting the refrigerant suction port 10b with the first
connection end 20a), the second flow control valve 36 is fully
opened, and the first flow control valves 32P-32R is throttled.
Also, the connection port 24b of the three-way switching valve 22
is closed while the connection ports 24a, 24c are opened. In this
arrangement, the compressor 10 initiates to be driven.
[0053] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature to one of high
pressure and high temperature, which is delivered from the
refrigerant delivery port 10a. The refrigerant is pressurized
adiabatically, i.e., without heat exchange with ambient air, which
is described by a constant-enthalpy line [1]-[2] in the p-h diagram
(pressure-enthalpy diagram) of FIG. 6.
[0054] The refrigerant of high pressure and high temperature flows
through the first switching member 16 and heats the ambient air in
the heat exchanger 12 to lower the temperature of the refrigerant.
The pressure thereof is kept almost constant but slightly declining
due to pressure loss in the heat exchanger 12 as the refrigerant is
cooled, which is represented by a almost flat line [2]-[3] in the
p-h diagram. Unlike the fluorocarbon-based refrigerant, the
refrigerant of carbon dioxide according to the present invention is
kept in a supercritical state at high temperature and lowers the
temperature without condensation.
[0055] The refrigerant from the heat exchanger 12 flows through the
second connection end 20b and the bypass pipe 34, while the flow
control valve 36 is fully opened, into each of the indoor units
6P-6R, in which throttling the flow control valves 32P-32R changes
(decompresses) the refrigerant to the two-phase vapor-liquid
refrigerant of low temperature and low pressure. The refrigerant is
decompressed at the flow control valves 32P-32R under the constant
enthalpy, which is represented by a vertical line [3]-[4] of the
p-h diagram.
[0056] As the two-phase vapor-liquid refrigerant of low temperature
and low pressure is changing to the vapor refrigerant of low
temperature and low pressure, it refrigerates (absorbs heat from)
the ambient air in the heat exchanger 28. The pressure of the
refrigerant is kept almost constant but slightly declining due to
pressure loss in the heat exchanger 28 as the refrigerant absorbs
heat, which is represented by a almost flat line [4]-[1] in the p-h
diagram.
[0057] The vapor refrigerant of low temperature and low pressure
from the heat exchanger 28 returns through the three-way switching
valves 22, the first connection end 20a, and the first switching
member 16, into the compressor 10.
[0058] It should be noted that while the pressure of the vapor
refrigerant immediately after coming out of the heat exchanger 28
becomes lower than that of the refrigerant just before coming in
the compressor 10 during transfer through the pipes, the vapor
refrigerant is represented by the same point [1] Similarly, while
the high pressure of the refrigerant just before the flow control
valve 32 is slightly less than that of the refrigerant right after
the heat exchanger 12, the refrigerant is represented by the same
point [3]. The slight pressure reduction of the refrigerant and the
pressure loss in the heat exchangers 12, 28 are observed also in
the heating operation mode, and the principally-cooling and
principally-heating operation modes, as will be described herein,
thus, duplicate explanation will be eliminated, unless
necessary.
Heating Operation Mode (FIGS. 3 and 7)>>
[0059] When all of the indoor units 6P-6R perform the heating
operation, the switching member 16 switches to the second flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with the first connection end 20a and by connecting
the refrigerant suction port 10b with one end 12a of the heat
exchanger 12), the second flow control valve 36 is fully opened,
and the first flow control valves 32P-32R is throttled. Also, the
connection port 24b of the three-way switching valve 22 is closed
while the connection ports 24a, 24c are opened. In this
arrangement, the compressor 10 initiates to be driven.
[0060] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature (point [1]) to one
of high pressure and high temperature, which is delivered from the
refrigerant delivery port 10a. The refrigerant of high pressure and
high temperature (point [2]) flows through the first switching
member 16, the first connection end 20a, and the three-way
switching valves 22 into each one of the heat exchangers 28 of the
indoor units 6P-6R. The refrigerant heats the ambient air in the
heat exchangers 28 thereby to lower the temperature of the
refrigerant (point [3]), and is decompressed by the flow control
valve 32 to be changed as the two-phase vapor-liquid refrigerant of
low temperature and low pressure (point [4]). Then, the refrigerant
from each of the indoor units 6P-6R flows through the bypass pipe
34 and the second connection end 20b to the other end 12b of the
heat exchanger 12. The two-phase vapor-liquid refrigerant
refrigerates (absorbs heat from) the ambient air in the heat
exchanger 12 to be the vapor refrigerant of low temperature and low
pressure (point [1]), which returns to the compressor 10 through
the switching member 16.
<<Principally Cooling Operation Mode (FIGS. 4 and
8)>>
[0061] When two of the indoor units 6P, 6Q perform the cooling
operation and one of the indoor unit 6R performs the heating
operation, the switching member 16 switches to the first flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with one end 12a of the heat exchanger 12 and by
connecting the refrigerant suction port 10b with the first
connection end 20a). Also, the second flow control valve 36 is
closed, and the first flow control valves 32P and 32Q are
throttled, while the valve 32R is fully opened. Further, each of
the three-way switching valves 22P and 22Q has the connection port
24b being closed and the connection ports 24a and 24c being opened.
The three-way switching valve 22R has the connection port 24a being
closed and the connection ports 24b and 24c being opened. In this
arrangement, the compressor 10 initiates to be driven.
[0062] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature (point [1]) to one
of high pressure and high temperature, which is delivered from the
refrigerant delivery port 10a. The refrigerant of high pressure and
high temperature (point [2]) flows through the first switching
member 16 to the heat exchanger 12, heating the ambient air in the
heat exchanger 12 thereby to lower the temperature of the
refrigerant (point [3]).
[0063] The refrigerant of high pressure from the heat exchanger 12
flows through the second connection end 20b and the three-way
switching valve 22R into the indoor unit 6R to heat the ambient air
in the heat exchanger 28 to lower the temperature of the
refrigerant (point [4]). Then, the refrigerant is decompressed by
the flow control valve 32P and 32Q to be the two-phase vapor-liquid
refrigerant of low temperature and low pressure (point [5]). The
refrigerant refrigerates (absorbs heat from) the ambient air in the
heat exchanger 23 of the indoor units 6P, 6Q, changing to the vapor
refrigerant of low temperature and low pressure (point [1]).
[0064] The refrigerant from the indoor units 6P, 6Q passes through
the three-way switching valve 22P and 22Q, the first connection end
20a, and the switching member 16r and returns to the compressor
10.
[0065] The refrigerant of carbon dioxide according to the present
invention can be kept in a supercritical state while flowing from
the refrigerant delivery port 10a of the compressor 10 through the
first switching member 16, the indoor heat exchanger 12, the indoor
unit 6R, and the flow control valves 32P and 32Q of the indoor
units 6P and 6Q. Therefore, noise and pressure pulsation can be
avoided or reduced, which might otherwise be generated at the flow
control valves 32P and 32Q of the indoor units 6P and 6Q.
[0066] In the meanwhile, as a comparative example, a conventional
air conditioner using the fluorocarbon-based refrigerant will be
described herein and illustrated in FIG. 10. The air conditioner 2'
includes the vapor-liquid separation device intervening in the
inter-unit pipe 18b within the relay device 8', and the bypass pipe
34 is connected to the liquid-phase port of the vapor-liquid
separation device 40.
[0067] When the conventional air conditioner performs in the
principally cooling operation mode, i.e., when two of the indoor
units 6P, 6Q perform the cooling operation and one of the indoor
unit 6R performs the heating operation, the switching member 16
switches to the first flow condition (by connecting the refrigerant
delivery port 10a of the compressor 10 with one end 12a of the heat
exchanger 12 and by connecting the refrigerant suction port 10b
with the first connection end 20a). Also, the second flow control
valve 36 and the first flow control valves 32P, 32Q are throttled,
while the valve 32R is fully opened. Further, each of the three-way
switching valves 22P, 22Q has the connection port 24b being closed
and the connection ports 24a, 24c being opened. The three-way
switching valve 22R has the connection port 24a being closed and
the connection ports 24b and 24c being opened. In this arrangement,
the compressor 10 initiates to be driven.
[0068] Pressurization by the compressor 10 changes the
fluorocarbon-based vapor refrigerant of low pressure and low
temperature (point [1]) to one of high pressure and high
temperature, which is delivered from the refrigerant delivery port
10a. The refrigerant of high pressure and high temperature flows
through the first switching member 16 to the heat exchanger 12, in
which the refrigerant heats the ambient air in the heat exchanger
12 to partially condense thereby to be the two-phase vapor-liquid
refrigerant of high pressure, since the pressure of the refrigerant
coming into the heat exchanger 12 is lower than the critical
pressure. The two-phase vapor-liquid refrigerant from the heat
exchanger 12 enters the vapor-liquid separation device 40. The
vapor refrigerant runs through the three-way valve 22R into the
heat exchanger 28 of the indoor unit 6R, in which the vapor
refrigerant heats the ambient air in the heat exchanger 28 to
condense, thereby changing to the liquid refrigerant of high
pressure that passes through the flow control valve 32R. Meanwhile,
another liquid refrigerant in the vapor-liquid separation device 40
flows through the flow control valve 36 and joins with the former
liquid refrigerant from the indoor unit 6R, both of which liquid
refrigerant come into the indoor units 6P, 6Q. Then, the
refrigerant is decompressed by the flow control valve 32P, 32Q,
changing to the two-phase vapor-liquid refrigerant of low
temperature and low pressure. The refrigerant refrigerates (absorbs
heat from) the ambient air in the heat exchanger 28, further
changing to the vapor refrigerant of low temperature and low
pressure. The refrigerant from the indoor units 6P, 6Q passes
through the three-way switching valve 22P, 22Q and the switching
member 16, and returns to the compressor 10.
[0069] The flow control valve 36 controls the flow amount of the
liquid refrigerant running from the vapor-liquid separation device
40 so that the vapor refrigerant running from the vapor-liquid
separation device 40 into the indoor unit 6R contains no liquid
refrigerant. Thus, the liquid refrigerant is decompressed when
passing through the flow control valve 36 and the bypass pipe 34.
As the liquid refrigerant running from the vapor-liquid separation
device 40 is the saturated refrigerant, it can be the two-phase
vapor-liquid refrigerant by depressurization, which causes noise
and pressure pulsation generated when the vapor-liquid refrigerant
passes the flow control valves 33P, 33Q of the indoor units 6P,
6Q.
[0070] To address the drawback, the conventional air conditioner 2'
requires a feature designed for overcooling the liquid refrigerant
running from the vapor-liquid separation device 40. In particular,
a second bypass pipe 42 is arranged adjacent the first bypass pipe
34, which has one end connected to a portion of the first bypass
pipe 34 downstream of the flow control valve 36 and the other end
connected to the inter-unit pipe 18a. Also, another flow control
valve 44 is provided intervening in the second bypass pipe 42. This
allows the liquid refrigerant at the flow control valve 44 to
expand (decompress) by throttling the flow control valve 44 thereby
to obtain the two-phase vapor-liquid refrigerant of low temperature
and low pressure. The second bypass pipe 42 with the vapor-liquid
refrigerant overcools the refrigerant through the first bypass pipe
34 in regions between the vapor-liquid separation device 40 and the
flow control valve 36 and between the flow control valve 36 and the
connection portion.
[0071] As above, when the fluorocarbon-based refrigerant is used in
the air conditioner, too many components have to be incorporated
into the relay device 8'.
[0072] On the contrary, according to the present embodiment of the
invention, a substantial number of components of the relay device
8' can be eliminated by using the refrigerant of carbon dioxide.
Also, fewer number of flow control valves improves controllability
of the cooling and heating capacity for the indoor heat exchangers
32P-32R.
[0073] It should be noted that while in the principally cooling
operation mode of the present embodiment, the flow control valve 36
is closed so that all of the refrigerant flows the indoor unit 6R
heating the room, the flow control valve 36 may be adjusted so that
a portion of the refrigerant passes through the first bypass pipe
34, bypassing the indoor unit 6R. This prevents increase of the
refrigerant flow, which may cause the refrigerant noise and the
erosion of the pipe.
<<Principally Heating Operation Mode (FIGS. 5 and
9)>>
[0074] When two of the indoor units 6P, 6Q perform the heating
operation and one of the indoor unit 6R performs the cooling
operation, the switching member 16 switches to the second flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with the first connection end 20a and by connecting
the refrigerant suction port 10b with one end 12a of the heat
exchanger 12). Also, the second flow control valve 36 is throttled,
and the first flow control valves 32P, 32Q are fully opened, while
the first flow control valve 32R is throttled. Further, each of the
three-way switching valves 22P, 22Q has the connection port 24b
being closed and the connection ports 24a, 24c being opened. The
three-way switching valve 22R has the connection port 24a being
closed and the connection ports 24b and 24c being opened. In this
arrangement, the compressor 10 initiates to be driven.
[0075] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature (point [1]) to one
of high pressure and high temperature, which is delivered from the
refrigerant delivery port 10a. The refrigerant of high pressure and
high temperature (point [2]) flows through the first switching
member 16 and the three-way switching valve 22P, 22Q to the heat
exchangers 28 of the indoor units 6P, 6Q, heating the ambient air
in the heat exchangers 28 thereby to lower the temperature of the
refrigerant (point [3]). After flowing through the heat exchangers
28 and the flow control valves 32P and 32Q of the indoor units 6P
and 6Q, a portion of the refrigerant runs towards the indoor unit
6R and the remaining portion thereof bypasses the indoor unit 6R
through the bypass pipe 34.
[0076] The refrigerant entering the indoor unit 6R expands
(decompresses) at the flow control valve 32R, changing to the
two-phase vapor-liquid refrigerant of low temperature and low
pressure (point [4]). Also, the refrigerant all or partially
evaporates to refrigerate the ambient air in the heat exchanger 28
(point [5]) and enters the three-way switching valves 22R. Although
not limited thereto, according to the present embodiment of FIG. 9,
the refrigerant passing out of the heat exchanger 28 (point
[0077] ) is the two-phase vapor-liquid refrigerant having the
dryness close to 1.0.
[0078] On the other hand, the remaining portion of the refrigerant
(point [3]) bypasses the indoor unit 6R through the bypass pipe 34
and expands (decompresses) at the flow control valve 36, changing
to the two-phase vapor-liquid refrigerant of low temperature and
low pressure (point [6]) Although not limited thereto, according to
the present embodiment of FIG. 9, the refrigerant passing out of
the flow control valve 36 (point [6]) has the pressure slightly
less than that of the refrigerant passing out of the heat exchanger
28 (point [5]).
[0079] The refrigerant passing out of the flow control valve 36 and
the refrigerant passing out of the three-way control valve 22R join
to be the two-phase vapor-liquid refrigerant (point [7]), which
flows through the second connection end 20b of the outdoor unit 4
to the heat exchanger 12. Also, the two-phase vapor-liquid
refrigerant refrigerates the ambient air in the heat exchanger 12,
changing to the vapor refrigerate (point [1]), which passes through
the switching member 16 back to the compressor 10.
[0080] As above, the air conditioner according to the present
embodiment controls the refrigerant flow passing through the indoor
unit that performs the cooling operation with adjustment of the
flow control valve 36, thereby improving the operation
efficiency.
EMBODIMENT 2
[0081] FIG. 11 illustrates the second embodiment of an air
conditioner according to the present invention. The outdoor unit 4A
of the air conditioner 2A includes a flow-path selecting member 52
in addition to the structure of the air conditioner 2 of the first
embodiment. The flow-path selecting member 52 is designed such that
the refrigerant flows from the outdoor unit 4A into the relay
device 8A always through the second connection end 20b, and from
the relay device 8A to the outdoor unit 4A always through the first
connection end 20a, regardless of the operation modes.
[0082] In particular, the flow-path selecting member 52 includes a
pair of check valves 54, 56, intervening in the pipes between the
first switching member 16 and the first connection end 20a, and
between the heat exchanger 12 and the second connection end 20b,
respectively. The check valve 54 allows the refrigerant to flow
only in a direction from the first connection end 20a to the
switching member 16, and the check valve 56 allows the refrigerant
to flow only in a direction from the heat exchanger 12 to the
second connection end 20b.
[0083] Also, the flow-path selecting member 52 includes a bypass
pipe 58 having one end connected to an intermediate point of the
pipe 14d between the switching member 16 and check valve 54 and the
other end connected to the second connection end 20b. A check valve
60 is provided intervening in the bypass pipe 58, which allows the
refrigerant to flow only in a direction from the switching member
16 to the second connection end 20b. Further, the flow-path
selecting member 52 includes a bypass pipe 62 having one end
connected to the first connection end 20a and the other end
connected to an intermediate point of the pipe 14e between the heat
exchanger 12 and the check valves 56. A check valve 60 is provided
intervening in the bypass pipe 62, which allows the refrigerant to
flow only in a direction from the first connection end 20a to the
heat exchanger 12.
[0084] The relay device 8A includes a second bypass pipe 66
connecting between the first bypass pipe 34 and the inter-unit pipe
18a, and a third flow control valve 68 intervening in the second
bypass pipe 66 for controlling the refrigerant flow running
therethrough.
[0085] Next, each of the operation modes performed by the air
conditioner 2A' so structured will be described herein.
<<Cooling Operation Mode>>
[0086] When all of the indoor units 6P-6R perform the cooling
operation, the switching member 16 switches to the first flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with one end 12a of the heat exchanger 12 and by
connecting the refrigerant suction port 10b with the first
connection end 20a), the second flow control valve 36 is fully
opened, and the first flow control valves 32P-32R is throttled,
while the third flow control valve 68 is closed. Also, the
connection ports 24b of the three-way switching valves 22 are
closed while the connection ports 24a, 24c are opened. In this
arrangement, the compressor 10 initiates to be driven.
[0087] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature to one of high
pressure and high temperature, which is delivered from the
refrigerant delivery port loan The refrigerant of high pressure and
high temperature flows through the first switching member 16 into
the heat exchanger 12, heating the ambient air in the heat
exchanger 12 thereby to lower the temperature of the refrigerant
without condensation. The refrigerant of high pressure from the
heat exchanger 12 flows through the check valve 56, the second
connection end 20b, and the first bypass pipe 34 (the second flow
control valve 36 is fully opened) to the indoor units 6P-6R, in
which the refrigerant expands (decompresses) at the flow control
valves 32P-32R, changing to the two-phase vapor-liquid refrigerant
of low temperature and low pressure. The refrigerant refrigerates
(absorbs heat from) the ambient air in the heat exchanger 28,
changing to the vapor refrigerant of low temperature and low
pressure. The refrigerant from the heat exchangers 28 of the indoor
units 6P-6R flows through the three-way switching valve 22P-22R and
the first connection end 20a. The refrigerant at the first
connection end 20a has pressure less than the refrigerant between
the heat exchanger 12 and the check valve 64 so that it is
automatically guided to pass through the check valve 54 and the
first switching member 16 back to the compressor 10.
<<Heating Operation Mode>>
[0088] When all of the indoor units 6P-6P, perform the heating
operation, the switching member 16 switches to the second flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with the first connection end 20a and by connecting
the refrigerant suction port 10b with one end 12a of the heat
exchanger 12), the second flow control valve 36 is fully opened,
and the first flow control valves 32P-32R is throttled while the
third flow control valve 68 is fully opened. Also, the connection
port 24a of the three-way switching valve 22 is closed while the
connection ports 24b, 24c are opened. In this arrangement, the
compressor 10 initiates to be driven.
[0089] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature to one of high
pressure and high temperature, which is delivered from the
refrigerant delivery port 10a. The refrigerant of high pressure and
high temperature flows through the first switching member 16, the
check valve 60, the second connection end 20b, and the three-way
switching valves 22 to each one of the heat exchangers 28 of the
indoor units 6P-6R. The refrigerant heats the ambient air in the
heat exchangers 28 to lower the temperature of the refrigerant, and
is decompressed by the flow control valve 32, changing to the
two-phase vapor-liquid refrigerant of low temperature and low
pressure. Then, the refrigerant from each of the indoor units 6P-6R
flows through the first bypass pipe 34 and the third flow control
valve 68 (the second bypass pipe 66) into the first connection end
20a. The refrigerant at the first connection end 20a has pressure
less than the refrigerant between the switching member 16 and the
check valve 54 so that it is automatically guided through the check
valve 64 to the other end 12b of the heat exchanger 12. The
two-phase vapor-liquid refrigerant refrigerates (absorbs heat from)
the ambient air in the heat exchanger 12, changing to the vapor
refrigerant of low temperature and low pressure, which runs through
the switching member 16 back to the compressor 10.
<<Principally Cooling Operation Mode>>
[0090] When two of the indoor units 6P, 6Q perform the cooling
operation and one of the indoor unit 6R performs the heating
operation, the switching member 16 switches to the first flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with one end 12a of the heat exchanger 12 and by
connecting the refrigerant suction port 10b with the first
connection end 20a). Also, the second and third flow control valves
36, 68 are closed, and the first flow control valves 32P, 32Q are
throttled, while the first flow control valve 32R is fully opened.
Further, each of the three-way switching valves 22P, 22Q has the
connection port 24b being closed and the connection ports 24a and
24c being opened. The three-way switching valve 22R has the
connection port 24a being closed and the connection ports 24b, 24c
being opened. In this arrangement, the compressor 10 initiates to
be driven.
[0091] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature to one of high
pressure and high temperature, which is delivered from the
refrigerant delivery port 10a. The refrigerant of high pressure and
high temperature flows through the first switching member 16 into
the heat exchanger 12, heating the ambient air in the heat
exchanger 12 thereby to lower the temperature of the refrigerant.
The refrigerant of high pressure from the heat exchanger 12 flows
through the check valve 56, the second connection end 20b, and the
three-way switching valve 22R into the indoor unit 6R, heating the
ambient air in the heat exchanger 28 thereby to lower the
temperature of the refrigerant. Then, the refrigerant is
decompressed by the flow control valve 32P, 32Q, changing to the
two-phase vapor-liquid refrigerant of low temperature and low
pressure. The refrigerant refrigerates (absorbs heat from) the
ambient air in the heat exchanger 28 of the indoor units 6P, 6Q,
changing to the two-phase vapor-liquid. refrigerant of low
temperature and low pressure. The refrigerant from the indoor units
6P, 6Q passes through the three-way switching valve 22P, 22Q into
the first connection end 20a. The refrigerant at the first
connection end 20a has pressure less than the refrigerant between
the heat exchanger 12 and the check valve 64 so that it is
automatically guided to pass through the check valve 54 and the
switching member 16 back to the compressor 10.
[0092] It should be noted that while in the principally cooling
operation mode of the second embodiment, the flow control valve 36
is closed so that all of the refrigerant flows into the indoor unit
6R heating the room, the flow control valve 36 may be adjusted so
that a portion of the refrigerant passes through the first bypass
pipe 34 bypassing the indoor unit 6R. This prevents increase of the
refrigerant flow, which may cause the refrigerant noise and the
erosion of the pipe.
<<Principally Heating Operation Mode>>
[0093] When two of the indoor units 6P, 6Q perform the heating
operation and one of the indoor unit 6R performs the cooling
operation, the switching member 16 switches to the second flow
condition (by connecting the refrigerant delivery port 10a of the
compressor 10 with the first connection end 20a and by connecting
the refrigerant suction port 10b with one end 12a of the heat
exchanger 12). Also, the second flow control valve 36 is closed,
and the first flow control valves 32P, 32Q are fully opened, while
the first flow control valve 32R and the third flow control valve
68 are throttled. Further, each of the three-way switching valves
22P, 22Q has the connection port 24a being closed and the
connection ports 24b, 24c being opened. The three-way switching
valve 22R has the connection port 24b being closed and the
connection ports 24a, 24c being opened. In this arrangement, the
compressor 10 initiates to be driven.
[0094] Pressurization by the compressor 10 changes the vapor
refrigerant of low pressure and low temperature to one of high
pressure and high temperature, which is delivered from the
refrigerant delivery port 10a. The refrigerant of high pressure and
high temperature flows through the first switching member 16 and
the three-way switching valve 22P, 22Q into the heat exchangers 28
of the indoor units 6P and 6Q, heating the ambient air in the heat
exchangers 28 thereby to lower the temperature of the refrigerant.
After flowing through the heat exchangers 28 and the flow control
valves 32P, 32Q of the indoor units 6P, 6Q, a portion of the
refrigerant runs towards the indoor unit 6R and the remaining
portion thereof passes through the bypass pipe 34.
[0095] The refrigerant entering the indoor unit 6R expands
(decompresses) at the flow control valve 32R, changing to the
two-phase vapor-liquid refrigerant of low temperature and low
pressure. Also, the refrigerant all or partially evaporates to
refrigerate the ambient air in the heat exchanger 28 and enters the
three-way switching valves 22R.
[0096] On the other hand, the remaining portion of the refrigerant
bypassing the indoor unit 6R passes through the first and second
bypass pipes 34, 66 and expands (decompresses) at the flow control
valve 68 to be two-phase vapor-liquid refrigerant of low
temperature and low pressure. The refrigerant passing out of the
flow control valve 68 joins with the refrigerant passing out of the
three-way control valve 22R to be the two-phase vapor-liquid
refrigerant, which flows into the first connection end 20a of the
outdoor unit 4. The refrigerant at the first connection end 20a has
pressure less than the refrigerant between the switching member 16
and the check valve 54 so that it is automatically guided to return
through the check valve 64 to the other end 12a of the heat
exchanger 12. The two-phase vapor-liquid refrigerant refrigerates
the ambient air in the heat exchanger 12 to change itself to be
vapor refrigerant of low temperature and low pressure in the heat
exchanger 12, which returns through the switching member 16 to the
compressor 10.
[0097] The air conditioner of the present embodiment has another
advantage in addition to those of the first embodiment. That is, a
pair of the inter-unit pipes connecting between the outdoor unit 4A
and the indoor unit 6P-6R can be designed such that the refrigerant
of high pressure flows only through one of the pipes 18b, and the
refrigerant of low pressure flows only through the other one of the
pipes 18a. Therefore, the inter-unit pipe 18a may have the pipe
wall thickness less than that of the inter-unit pipe 18b.
[0098] The three-way switching valve is used in the second
embodiment. Alternatively, a pair of two-way valves 22, 23 may be
adapted as illustrated in FIG. 12. In particular, the two-way valve
22 has one end connected to the inter-unit pipe 18a and the second
bypass pipe 66, and the other end connected to the indoor unit 28.
Also, the another two-way valve 23 has one end connected to the
inter-unit pipe 18b and the other end connected to the indoor unit
28. To this end, similar to the second embodiment, the flow
directions of the refrigerant running through the inter-unit pipes
18a, 18b (and the two-way valves 22, 23) can be kept the same
regardless the operation modes.
[0099] Although not limited thereto, several embodiments have been
explained above solely for purpose to describe the present
invention, and the embodiments can be changed and modified without
departing the scope of the present invention. For example, the
switching member may have any other structures rather than the
three-way control valves 22P-22R, for selectively connecting the
indoor heat exchanger 28 with the pipe 18a or 18b.
[0100] Also, in the second embodiment, the flow-path selecting
member 52 may have any other structures for allowing the
refrigerant to flow from the outdoor unit 4A to the relay device BA
only through the connection end 20b and from the relay device BA to
the outdoor unit 4A only through the connection end 20a, in which
the present invention is not limited to the structure shown in FIG.
11. Thus, when the switching member 16 switches to the first flow
condition by connecting the refrigerant delivery port 10a of the
compressor 10 with one end 12a of the heat exchanger 12 and by
connecting the refrigerant suction port 10b with the first
connection end 20a, the flow-path selecting member 52 guides the
refrigerant from the end 12b of the heat exchanger 12 to the
connection end 20b and blocks it to the connection end 12a. Also,
when the switching member 16 switches to the second flow condition
by connecting the refrigerant delivery port 10a of the compressor
10 with the first connection end 20a and by connecting the
refrigerant suction port 10b with one end 12a of the heat exchanger
12, the flow-path selecting member 52 guides the refrigerant from
the compressor 10 to the connection end 20b and blocks it to the
connection end 12a. Any types of the flow-path selecting members
having such structures are included in the present invention.
[0101] In the above embodiments, carbon dioxide itself is used as
the refrigerant, however, any composites having main ingredient of
carbon dioxide may be used as the refrigerant.
[0102] The term "unit" in the indoor and outdoor units is not
intended to describe that all components are physically provided
within or on the same housing. For instance, the structure having
the flow control valve of the indoor unit located at a position
remote from the housing in which the indoor heat exchanger 28 is
provided, also falls within the scope of the present invention.
Also, a plurality of pairs of outdoor heat exchangers and the
compressors may be provided within the outdoor unit so that the
refrigerant from each pairs of outdoor heat exchangers and the
compressors join to flow from one of the inter-unit pipes, and the
refrigerant from the other end of the inter-unit pipes is split to
each pair of outdoor heat exchangers and the compressors.
* * * * *