U.S. patent application number 12/377447 was filed with the patent office on 2010-11-04 for refrigeration system.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Masahide Higuchi, Satoshi Ishikawa, Masanori Masuda.
Application Number | 20100275632 12/377447 |
Document ID | / |
Family ID | 39135851 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100275632 |
Kind Code |
A1 |
Ishikawa; Satoshi ; et
al. |
November 4, 2010 |
REFRIGERATION SYSTEM
Abstract
A refrigeration system includes a compression mechanism, a
radiator, an expansion mechanism, an evaporator and a .pi.-type
silencer 20. The .pi.-type silencer includes a first silencing
space, a second silencing space and a first communication path. The
first communication path allows the first silencing space and the
second silencing space to be communicated. Additionally, the
.pi.-type silencer is incorporated in at least one of a section
between a refrigerant discharge side of the compression mechanism
and an inlet side of the radiator, and a section between an outlet
side of the evaporator and a refrigerant suction side of the
compression mechanism.
Inventors: |
Ishikawa; Satoshi; (
Fukuoka, JP) ; Masuda; Masanori; ( Osaka, JP)
; Higuchi; Masahide; (Shiga, JP) |
Correspondence
Address: |
GLOBAL IP COUNSELORS, LLP
1233 20TH STREET, NW, SUITE 700
WASHINGTON
DC
20036-2680
US
|
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
39135851 |
Appl. No.: |
12/377447 |
Filed: |
August 28, 2007 |
PCT Filed: |
August 28, 2007 |
PCT NO: |
PCT/JP2007/066615 |
371 Date: |
February 13, 2009 |
Current U.S.
Class: |
62/296 ;
62/498 |
Current CPC
Class: |
F25B 2313/02741
20130101; F25B 13/00 20130101; F25B 31/02 20130101; F25B 9/008
20130101; F04B 39/0055 20130101; F25B 2500/12 20130101 |
Class at
Publication: |
62/296 ;
62/498 |
International
Class: |
F25D 23/00 20060101
F25D023/00; F25B 1/00 20060101 F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 30, 2006 |
JP |
2006-233673 |
Claims
1. A refrigeration system filled with carbon dioxide as a
refrigerant, the refrigeration system comprising: a compression
mechanism configured to compress the refrigerant; a radiator
configured to radiate heat from the refrigerant that is discharged
from the compression mechanism; an expansion mechanism configured
to depressurize the refrigerant that flows out from the radiator;
an evaporator configured to evaporate the refrigerant that flows
out from the expansion mechanism; and a .pi.-type silencer that
includes a first silencing space, a second silencing space and a
first communication path that allows the first silencing space and
the second silencing space to be communicated, the .pi.-type
silencer being incorporated in at least one of a section between a
refrigerant discharge side of the compression mechanism and an
inlet side of the radiator, and a section between an outlet side of
the evaporator and a refrigerant suction side of the compression
mechanism.
2. The refrigeration system according to claim 1, wherein the
compression mechanism is a rotary compression mechanism, and a
length of the first communication path is longer than
S.sub.1/2(1/V.sub.1+1/V.sub.2)(c/.pi.N.sub.min).sup.2 (where
S.sub.1 is a cross-sectional area of the first communication path,
V.sub.1 is a volume of the first silencing space, V.sub.2 is a
volume of the second silencing space, c is a speed of N.sub.min
sound in the refrigerant, .pi. is pi, and is a minimum number of
rotations of the rotary compression mechanism).
3. The refrigeration system according to claim 1, wherein a length
of the first communication path is shorter than c/2f.sub.t (where c
is a speed of sound in the refrigerant and f.sub.t is a target
reduction highest frequency).
4. The refrigeration system according to claim 1, wherein the first
silencing space is a space inside an oil separator or an
accumulator.
5. The refrigeration system according to claim 1, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
6. The refrigeration system according to claim 2, wherein the
length of the first communication path is shorter than c/2f.sub.t
(where c f.sub.t is a target reduction highest frequency).
7. The refrigeration system according to claim 6, wherein the first
silencing space is a space inside an oil separator or an
accumulator.
8. The refrigeration system according to claim 7, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
9. The refrigeration system according to claim 6, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
10. The refrigeration system according to claim 2, wherein the
first silencing space is a space inside an oil separator or an
accumulator.
11. The refrigeration system according to claim 10, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
12. The refrigeration system according to claim 2, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
13. The refrigeration system according to claim 3, wherein the
first silencing space is a space inside an oil separator or an
accumulator.
14. The refrigeration system according to claim 13, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
15. The refrigeration system according to claim 3, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
16. The refrigeration system according to claim 4, wherein the
.pi.-type silencer further includes a third silencing space and a
second communication path that allows the second silencing space
and the third silencing space to be communicated.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigeration system and
particularly to a refrigeration system that can reduce pressure
pulsation.
BACKGROUND ART
[0002] In recent years, refrigeration systems that employ carbon
dioxide as a refrigerant have become commoditized. However, when
carbon dioxide is employed as a refrigerant in a refrigeration
system in this manner, there arises the problem that the density of
the refrigerant and the speed of sound in the refrigerant become
larger and pressure pulsation inevitably becomes larger. In order
to counter this problem, in recent years, various methods of
reducing pressure pulsation in refrigeration systems have been
proposed (e.g., see patent citation 1, patent citation 2,
non-patent citation 1 and non-patent citation 2).
[0003] Patent Citation 1: JP-A No. 6-10875
[0004] Patent Citation 2: JP-A No. 2004-218934
[0005] Non-Patent Citation 1: Sakae Yamada and Iwao tani, "Orifisu
oyobi .pi.-gata hairetsu k kis ni yoru myakud jokyo", Transactions
of the Japan Society of Mechanical Engineers (Second Part),
December 1968, Vol. 34, No. 268, pp. 2139-2145.
[0006] Non-Patent Citation 2: The Japan Society of Mechanical
Engineers, editor, "Jirei ni manabu ry tai kanren shind ", First
Edition, Gihodo Shuppan Co., Ltd., Sep. 20, 2003, pp. 190-193.
DISCLOSURE OF THE INVENTION
Technical Problem
[0007] It is an object of the present invention to sufficiently
reduce pressure pulsation in a refrigeration system that employs
carbon dioxide and the like as a refrigerant.
Solution to the Problem
[0008] A refrigeration system according to a first aspect of the
present invention is the refrigeration system that is filled with
carbon dioxide as a refrigerant and comprises a compression
mechanism, a radiator, an expansion mechanism, an evaporator and
.pi.-type silencer. The compression mechanism compresses the
refrigerant. The radiator causes the refrigerant that is discharged
from the compression mechanism to radiate heat. The expansion
mechanism depressurizes the refrigerant that flows out from the
radiator. The evaporator causes the refrigerant that flows out from
the expansion mechanism to evaporate. The .pi.-type silencer
includes a first silencing space, a second silencing space and a
first communication path. The first communication path allows the
first silencing space and the second silencing space to be
communicated. Additionally, the .pi.-type silencer is incorporated
in at least one of a section between a refrigerant discharge side
of the compression mechanism and an inlet side of the radiator and
a section between an outlet side of the evaporator and a
refrigerant suction side of the compression mechanism.
[0009] In this refrigeration system, the .pi.-type silencer is
incorporated in at least one of a section between a refrigerant
discharge side of the compression mechanism and an inlet side of
the radiator and a section between an outlet side of the evaporator
and a refrigerant suction side of the compression mechanism. For
this reason, in this refrigeration system, pressure pulsation can
be sufficiently reduced even when carbon dioxide is employed as a
refrigerant.
[0010] A refrigeration system according to a second aspect of the
present invention is the refrigeration system according to the
first aspect of the present invention, wherein the compression
mechanism is a rotary compression mechanism whose minimum number of
rotations is N.sub.min. Additionally, the length of the first
communication path is longer than
S.sub.1/2(1/V.sub.1+1V.sub.2)(c/.pi.N.sub.min).sup.2 (where S.sub.1
is the cross-sectional area of the communication path, V.sub.1 is
the volume of the first silencing space, V.sub.2 is the volume of
the second silencing space, c is the speed of sound in the
refrigerant, .pi. is pi, and N.sub.min is the minimum number of
rotations of the compression mechanism).
[0011] Incidentally, a cutoff frequency f of the .pi.-type silencer
is expressed by the following expression (1).
f=c/.pi. {S.sub.1/21.sub.1(1/V.sub.1+1/V.sub.2)} (1)
[0012] (Here, c is the speed of sound in the refrigerant, .pi. is
pi, S.sub.1 is the cross-sectional area of the communication path,
1.sub.1 is the length of the communication path, V.sub.1 is the
volume of the first silencing space, and V.sub.2 is the volume of
the second silencing space.)
[0013] Here, in order to make the cutoff frequency f equal to or
less than the minimum number of rotations of the compression
mechanism, it is necessary to satisfy the following expression
(2).
c/.pi. {S.sub.1/21.sub.1(1/V.sub.1+1/V.sub.2)}<N.sub.min (2)
[0014] Additionally, when this inequality expression (2) is solved
in regard to 1.sub.1, it becomes the following expression (3).
1.sub.i>S.sub.1/2(1/V.sub.1+1/V.sub.2)(c/.pi.N.sub.min).sup.2
(3)
[0015] In this refrigeration system, the minimum number of
rotations of the compression mechanism is N.sub.min and the length
of the first communication path is longer than
S.sub.1/2(1/V.sub.1+1/V.sub.2)(c/.pi.N.sub.min).sup.2. In other
words, in this refrigeration system, the condition of the above
inequality expression (3) is satisfied. For this reason, in this
refrigeration system, the cutoff frequency of the .pi.-type
silencer can be made equal to or less than the minimum number of
rotations of the compression mechanism.
[0016] A refrigeration system according to a third aspect of the
present invention is the refrigeration system according to the
first aspect or the second aspect of the present invention, wherein
the length of the first communication path is shorter than
c/2f.sub.t (where c is the speed of sound in the refrigerant and
f.sub.t is a target reduction highest frequency). Incidentally, a
decay rate .sigma. of the .pi.-type silencer is expressed by the
following expression (4).
.sigma. = [ { cos ( 1 1 .omega. / c ) - V 1 .omega.sin ( 1 1
.omega. / c ) / cS 1 } 2 + 1 / S 2 { ( V 1 + V 2 ) .omega.cos ( 1 1
.omega. / c ) / c + S 1 sin ( 1 1 .omega. / c ) - V 1 V 2 .omega. 2
sin ( 1 1 .omega. / c ) / c 2 S 1 } 2 ] ( 4 ) ##EQU00001##
[0017] (Here, 1.sub.1 is the length of the communication path,
.omega. is pulsation angular frequency, c is the speed of sound in
the refrigerant, S.sub.1 is the cross-sectional area of the
communication path, S is the cross-sectional area of a refrigerant
passage that is communicated with the .pi.-type silencer, V.sub.1
is the volume of the first silencing space, and V.sub.2 is the
volume of the second silencing space.)
[0018] Here, for example, assuming that V.sub.1=300 cc, V.sub.2=300
cc, S=0.785 cm.sup.2, S.sub.1=0.785 cm.sup.2, c=230 m/s and
1.sub.1=0.3 m, when the decay rate a is calculated from expression
(4), a tendency appears where the decay rate a first decreases and
thereafter again increases in accompaniment with an increase in the
frequency (in other words, a minimum value exists). Additionally,
this frequency region has a tendency to drop as 1.sub.1 becomes
longer. The frequency that corresponds to the minimum value of the
decay rate a corresponds to the frequency at which resonance arises
in the communication path (below, this will be called a resonance
frequency f.sub.r) and is expressed by the following expression
(5).
f.sub.r=c/21.sub.1 (5)
[0019] Here, in order to reduce the frequency that is smaller than
the target reduction highest frequency f.sub.t, it is necessary to
satisfy the following expression (6).
c/21.sub.1>f.sub.t (6)
[0020] Additionally, when this inequality expression (6) is solved
in regard to 1.sub.1, it becomes the following expression (7).
1.sub.1<c/2f.sub.t (7)
[0021] In this refrigeration system, the length of the first
communication path is shorter than c/2f.sub.t. In other words, in
this refrigeration system, the condition of the above inequality
expression (7) is satisfied. For this reason, in this refrigeration
system, the frequency that is smaller than the target reduction
highest frequency f.sub.t can be reduced.
[0022] A refrigeration system according to a fourth aspect of the
present invention is the refrigeration system according to any of
the first aspect to the third aspect of the present invention,
wherein the first silencing space is a space inside an oil
separator or an accumulator.
[0023] In this refrigeration system, the space inside an oil
separator or an accumulator serves as the first silencing space.
For this reason, this refrigeration system can be simplified.
[0024] A refrigeration system according to a fifth aspect of the
present invention is the refrigeration system according to any of
the first aspect to the fourth aspect of the present invention,
wherein the .pi.-type silencer further includes a third silencing
space and a second communication path that allows the second
silencing space and the third silencing space to be
communicated.
[0025] In this refrigeration system, the third silencing space and
the second communication path are disposed. For this reason, in
this refrigeration system, pressure pulsation can be reduced even
more.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0026] In the refrigeration system according to the first aspect of
the present invention, pressure pulsation can be sufficiently
reduced even when carbon dioxide is employed as a refrigerant.
[0027] In the refrigeration system according to the second aspect
of the present invention, the cutoff frequency of the .pi.-type
silencer can be made equal to or less than the minimum number of
rotations of the compression mechanism.
[0028] In the refrigeration system according to the third aspect of
the present invention, a frequency that is smaller than the target
reduction highest frequency f.sub.t can be reduced.
[0029] The refrigeration system according to the fourth aspect of
the present invention can be simplified.
[0030] In the refrigeration system according to the fifth aspect of
the present invention, pressure pulsation can be reduced even
more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a diagram of a refrigerant circuit of an air
conditioner pertaining to an embodiment of the present
invention;
[0032] FIG. 2 is a longitudinal sectional diagram of .pi.-type
silencer that is incorporated in the refrigerant circuit of the air
conditioner pertaining to the embodiment of the present
invention;
[0033] FIG. 3 is a longitudinal sectional diagram of .pi.-type
silencer pertaining to modification A;
[0034] FIG. 4 is a longitudinal sectional diagram of .pi.-type
silencer pertaining to modification A;
[0035] FIG. 5 is a longitudinal sectional diagram of .pi.-type
silencer pertaining to modification B;
[0036] FIG. 6 is a longitudinal sectional diagram of a .pi.-type
silencer pertaining to modification B;
[0037] FIG. 7 is a longitudinal sectional diagram of a .pi.-type
silencer pertaining to modification B;
[0038] FIG. 8 is a longitudinal sectional diagram of a .pi.-type
silencer pertaining to modification C;
[0039] FIG. 9 is a longitudinal sectional diagram of .pi.-type
silencer pertaining to modification D;
[0040] FIG. 10 is a longitudinal sectional diagram of .pi.-type
silencer pertaining to modification E;
[0041] FIG. 11 is a longitudinal sectional diagram of a .pi.-type
silencer pertaining to modification F;
[0042] FIG. 12 is a longitudinal sectional diagram of a .pi.-type
silencer pertaining to modification F; and
[0043] FIG. 13 is a longitudinal sectional diagram of .pi.-type
silencer pertaining to modification G.
EXPLANATION OF THE REFERENCE NUMERALS
[0044] 1 Air Conditioner (Refrigeration System) [0045] 11
Compressor (Compression Mechanism) [0046] 13 Outdoor Heat Exchanger
(Radiator, Evaporator) [0047] 15 First Electrically Powered
Expansion Valve (Expansion Mechanism) [0048] 17 Second Electrically
Powered Expansion Valve (Expansion Mechanism) [0049] 31 Indoor Heat
Exchanger (Radiator, Evaporator) [0050] 20, 20a, 20b, 20c, 20d,
20e, 20f, 20g, 20h, 20i, 20j, 20k .pi.-type Silencer [0051] 201,
201c, 201i First Silencing Space [0052] 202, 202c, 202i Second
Silencing Space [0053] 203, 203a, 203b, 203c, 203f, 203g, 203i,
203j, 203k Communication Path (First Communication Path)
BEST MODE FOR CARRYING OUT THE INVENTION
Configuration of Air Conditioner
[0054] FIG. 1 shows a general refrigerant circuit 2 of an air
conditioner 1 pertaining to an embodiment of the present
invention.
[0055] The air conditioner 1 uses carbon dioxide as a refrigerant,
is capable of cooling operation and heating operation, and is
mainly configured by the refrigerant circuit 2, blower fans 26 and
32, a controller 23, a high-pressure pressure sensor 21, a
temperature sensor 22, an intermediate-pressure pressure sensor 24
and the like.
[0056] The refrigerant circuit 2 is mainly equipped with a
compressor 11, a .pi.-type silencer 20, a four-way switch valve 12,
an outdoor heat exchanger 13, a first electrically powered
expansion valve 15, a liquid receiver 16, a second electrically
powered expansion valve 17 and an indoor heat exchanger 31, and the
devices are, as shown in FIG. 1, interconnected via refrigerant
pipes.
[0057] Additionally, in the present embodiment, the air conditioner
1 is a discrete-type air conditioner and may also be said to be
configured by: an indoor unit 30 that mainly includes the indoor
heat exchanger 31 and the indoor fan 32; an outdoor unit 10 that
mainly includes the compressor 11, the .pi.-type silencer 20, the
four-way switch valve 12, the outdoor heat exchanger 13, the first
electrically powered expansion valve 15, the liquid receiver 16,
the second electrically powered expansion valve 17, the
high-pressure pressure sensor 21, the intermediate-pressure
pressure sensor 24, the temperature sensor 22 and the controller
23; a first communication pipe 41 that interconnects a refrigerant
liquid pipe of the indoor unit 30 and a refrigerant liquid pipe of
the outdoor unit 10; and a second communication pipe 42 that
interconnects a refrigerant gas pipe of the indoor unit 30 and a
refrigerant gas pipe of the outdoor unit 10. It will be noted that
the refrigerant liquid pipe of the outdoor unit 10 and the first
communication pipe 41 are interconnected via a first close valve 18
of the outdoor unit 10 and that the refrigerant gas pipe of the
outdoor unit 10 and the second communication pipe 42 are
interconnected via a second close valve 19 of the outdoor unit
10.
(1) Indoor Unit
[0058] The indoor unit 30 mainly includes the indoor heat exchanger
31, the indoor fan 32 and the like.
[0059] The indoor heat exchanger 31 is a heat exchanger for causing
heat exchange between the refrigerant and room air that is air
inside an air-conditioned room.
[0060] The indoor fan 32 is a fan for taking the air inside the
air-conditioned room into the inside of the unit 30 and blowing out
air-conditioned air, which is air after heat has been exchanged
with the refrigerant via the indoor heat exchanger 31, back inside
the air -conditioned room.
[0061] Additionally, because the indoor unit 30 employs this
configuration, the indoor unit 30 is capable, during cooling
operation, of generating air-conditioned air (cool air) by causing
heat to be exchanged between the room air that has been taken
inside by the indoor fan 32 and liquid refrigerant that flows
through the indoor heat exchanger 31 and is capable, during heating
operation, of generating air-conditioned air (warm air) by causing
heat to be exchanged between the room air that has been taken
inside by the indoor fan 32 and supercritical refrigerant that
flows through the indoor heat exchanger 31.
(2) Outdoor Unit
[0062] The outdoor unit 10 mainly includes the compressor 11, the
.pi.-type silencer 20, the four-way switch valve 12, the outdoor
heat exchanger 13, the first electrically powered expansion valve
15, the liquid receiver 16, the second electrically powered
expansion valve 17, the outdoor fan 26, the controller 23, the
high-pressure pressure sensor 21, the temperature sensor 22, the
intermediate-pressure pressure sensor 24 and the like.
[0063] The compressor 11 is a device for sucking in low-pressure
gas refrigerant that flows through a suction pipe, compressing the
low-pressure gas refrigerant to a supercritical state, and
thereafter discharging the supercritical refrigerant to a discharge
pipe. It will be noted that, in the present embodiment, the
compressor 11 is an inverter rotary-type compressor.
[0064] The .pi.-type silencer 20 is, as shown in FIG. 1, disposed
between a discharge side of the compressor 11 and the four-way
switch valve 12. The .pi.-type silencer 20 is, as shown in FIG. 2,
configured by a first silencing space 201, a second silencing space
202 and a communication path 203 that allows the first silencing
space 201 and the second silencing space 202 to be communicated. It
will be noted that, in the air conditioner 1 pertaining to the
present embodiment, a discharge path of the compressor 11 is
connected to the first silencing space 201 via a first refrigerant
passage 204 and that a heat transfer path of the outdoor heat
exchanger 13 or the indoor heat exchanger 31 is connected to the
second silencing space 202 via a second refrigerant passage 205. In
other words, the refrigerant always flows in the order of the first
silencing space 201.fwdarw.the communication path 203.fwdarw.the
second silencing space 202. The first silencing space 201 is a
substantially cylindrical space, with the refrigerant passage 204
being connected to the upper end thereof in the axial direction and
the communication path 203 being connected to the lower end thereof
in the axial direction. The second silencing space 202 is a
substantially cylindrical space, with the communication path 203
being connected to the upper end thereof in the axial direction and
the refrigerant passage 205 being connected to the lower end
thereof in the axial direction. The communication path 203 is a
substantially cylindrical passage whose radius is smaller than the
radii of the first silencing space 201 and the second silencing
space 202, and the first silencing space 201 and the second
silencing space 202 are connected to both sides of the
communication path 203. It will be noted that, in the .pi.-type
silencer 20 pertaining to the present embodiment, the axes of the
first silencing space 201, the second silencing space 202 and the
communication path 203 are superposed. Additionally, the length of
the communication path 203 is longer than
S.sub.1/2(1/V.sub.1+1N.sub.2)(c/.pi.N.sub.min).sup.2 and shorter
than c/2f.sub.t. Here, S.sub.1 is the cross-sectional area of the
communication path 203, V.sub.1 is the volume of the first
silencing space 201, V.sub.2 is the volume of the second silencing
space 202, c is the speed of sound in carbon dioxide (when the
pressure is 10 MPa, the density becomes 221.6 kg/m.sup.3 and the
speed of sound becomes 252 m/sec), .pi. is pi, N.sub.min is the
minimum number of rotations of the compressor 11, and f.sub.t is a
target reduction highest frequency. It will be noted that, in the
air conditioner 1 pertaining to the present embodiment, the
.pi.-type silencer 20 is housed in the outdoor unit 10 such that
the first silencing space 201 and the second silencing space 202
are arranged one above the other along the vertical direction.
[0065] The four-way switch valve 12 is a valve for switching the
flow direction of the refrigerant in correspondence to each
operation and is capable, during cooling operation, of
interconnecting the discharge side of the compressor 11 and a high
temperature side of the outdoor heat exchanger 13 and also
interconnecting the suction side of the compressor 11 and a gas
side of the indoor heat exchanger 31 and is capable, during heating
operation, of interconnecting the discharge side of the compressor
11 and the second close valve 19 and also interconnecting the
suction side of the compressor 11 and a gas side of the outdoor
heat exchanger 13.
[0066] The outdoor heat exchanger 13 is capable, during cooling
operation, of using air outside the air-conditioned room as a heat
source to cool the high-pressure supercritical refrigerant that has
been discharged from the compressor 11 and is capable, during
heating operation, of evaporating the liquid refrigerant that
returns from the indoor heat exchanger 31.
[0067] The first electrically powered expansion valve 15 is for
depressurizing the supercritical refrigerant (during cooling
operation) that flows out from a low temperature side of the
outdoor heat exchanger 13 or the liquid refrigerant (during heating
operation) that flows in through the liquid receiver 16.
[0068] The liquid receiver 16 is for storing surplus refrigerant in
accordance with the operating mode and the air conditioning
load.
[0069] The second electrically powered expansion valve 17 is for
depressurizing the liquid refrigerant (during cooling operation)
that flows in through the liquid receiver 16 or the supercritical
refrigerant (during heating operation) that flows out from a low
temperature side of the indoor heat exchanger 31.
[0070] The outdoor fan 26 is a fan for taking outdoor air into the
inside of the unit 10 and discharging the air after the air has
exchanged heat with the refrigerant via the outdoor heat exchanger
13.
[0071] The high-pressure pressure sensor 21 is disposed on the
discharge side of the compressor 11.
[0072] The temperature sensor 22 is disposed on the outdoor heat
exchanger side of the first electrically powered expansion valve
15.
[0073] The intermediate-pressure pressure sensor 24 is disposed
between the first electrically powered expansion valve 15 and the
liquid receiver 16.
[0074] The controller 23 is communicably connected to the
high-pressure pressure sensor 21, the temperature sensor 22, the
intermediate-pressure pressure sensor 24, the first electrically
powered expansion valve 15, the second electrically powered
expansion valve 17 and the like and controls the openings of the
first electrically powered expansion valve 15 and the second
electrically powered expansion valve 17 on the basis of temperature
information that is sent from the temperature sensor 22,
high-pressure pressure information that is sent from the
high-pressure pressure sensor 21 and intermediate-pressure pressure
information that is sent from the intermediate-pressure pressure
sensor 24.
<Operation of Air Conditioner>
[0075] Operation of the air conditioner 1 will be described using
FIG. 1. The air conditioner 1 is, as mentioned above, capable of
performing cooling operation and heating operation.
(1) Cooling Operation
[0076] During cooling operation, the four-way switch valve 12 is in
the state indicated by the solid lines in FIG. 1, that is, a state
where the discharge side of the compressor 11 is connected to the
high temperature side of the outdoor heat exchanger 13 and where
the suction side of the compressor 11 is connected to the second
close valve 19. Further, at this time, the first close valve 18 and
the second close valve 19 are opened.
[0077] When the compressor 11 is started in this state of the
refrigerant circuit 2, gas refrigerant is sucked into the
compressor 11, is compressed to a supercritical state, is
thereafter sent to the outdoor heat exchanger 13 via the four-way
switch valve 12, and is cooled in the outdoor heat exchanger 13. It
will be noted that, at this time, pressure pulsation of the
refrigerant is dampened by the .pi.-type silencer 20.
[0078] Then, the supercritical refrigerant that has been cooled is
sent to the first electrically powered expansion valve 15. Then,
the supercritical refrigerant that has been sent to the first
electrically powered expansion valve 15 is depressurized to a
saturated state and is thereafter sent to the second electrically
powered expansion valve 17 via the liquid receiver 16. The
refrigerant in the saturated state that has been sent to the second
electrically powered expansion valve 17 is depressurized, becomes
liquid refrigerant, is thereafter supplied to the indoor heat
exchanger 31 via the first close valve 18, cools the room air, is
evaporated and becomes gas refrigerant.
[0079] Then, the gas refrigerant is sucked back into the compressor
11 via the second close valve 19 and the four-way switch valve 12.
In this manner, cooling operation is performed.
(2) Heating Operation
[0080] During heating operation, the four-way switch valve 12 is in
the state indicated by the broken lines in FIG. 1, that is, a state
where the discharge side of the compressor 11 is connected to the
second close valve 19 and where the suction side of the compressor
11 is connected to the gas side of the outdoor heat exchanger 13.
Further, at this time, the first close valve 18 and the second
close valve 19 are opened.
[0081] When the compressor 11 is started in this state of the
refrigerant circuit 2, gas refrigerant is sucked into the
compressor 11, is compressed to a supercritical state, and is
thereafter supplied to the indoor heat exchanger 31 via the
four-way switch valve 12 and the second close valve 19. It will be
noted that, at this time, pressure pulsation of the refrigerant is
dampened by the .pi.-type silencer 20.
[0082] Then, the supercritical refrigerant heats the room air in
the indoor heat exchanger 31 and is cooled. The supercritical
refrigerant that has been cooled is sent to the second electrically
powered expansion valve 17 through the first close valve 18. The
supercritical refrigerant that has been sent to the second
electrically powered expansion valve 17 is depressurized to a
saturated state and is thereafter sent to the first electrically
powered expansion valve 15 via the liquid receiver 16. The
refrigerant in the saturated state that has been sent to the first
electrically powered expansion valve 15 is depressurized, becomes
liquid refrigerant, is thereafter sent to the outdoor heat
exchanger 13, is evaporated in the outdoor heat exchanger 13 and
becomes gas refrigerant. Then, the gas refrigerant is sucked back
into the compressor 11 via the four-way switch valve 12. In this
manner, heating operation is performed.
<Characteristics of Air Conditioner>
[0083] (1)
[0084] In the air conditioner 1 pertaining to the present
embodiment, the .pi.-type silencer 20 is connected to the discharge
pipe of the compressor 11. For this reason, in the air conditioner
1, pressure pulsation can be sufficiently reduced.
(2)
[0085] In the air conditioner 1 pertaining to the present
embodiment, the .pi.-type silencer 20 is housed in the outdoor unit
10 such that the first silencing space 201 and the second silencing
space 202 are arranged one above the other along the vertical
direction. For this reason, in the air conditioner 1, refrigerating
machine oil can be prevented from collecting in the .pi.-type
silencer 20.
(3)
[0086] In the .pi.-type silencer 20 pertaining to the present
embodiment, the length of the communication path is longer than
S.sub.1/2(1/V.sub.1+1/V.sub.2)(c/.pi.N.sub.min).sup.2 and shorter
than c/2f.sub.t. For this reason, in the air conditioner 1, the
cutoff frequency of the .pi.-type silencer 20 can be made equal to
or less than the minimum number of rotations of the compression
mechanism, and a frequency that is smaller than the target
reduction highest frequency f.sub.t can be reduced.
<Modifications>
(A)
[0087] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 that
includes the communication path 203 that extends along the axial
direction of the first silencing space 201 from the lower end of
the first silencing space 201 and is connected to the upper end of
the second silencing space 202, but instead of the .pi.-type
silencer 20, there may also be employed a .pi.-type silencer 20a
such as shown in FIG. 3. In the .pi.-type silencer 20a, a
communication path 203a that extends along the axial direction of
the first silencing space 201 from the lower end of the first
silencing space 201 penetrates the upper end of the second
silencing space 202 and is inserted into the inside of the second
silencing space 202. When the .pi.-type silencer 20a is employed,
just the communication path can be extended long without having to
change the size of the entire .pi.-type silencer. In a .pi.-type
silencer, the longer the communication path is, the larger the
pressure pulsation reduction effect becomes. In other words, the
pressure pulsation reduction effect can be made larger without
having to change the size of the entire .pi.-type silencer.
[0088] Further, there may also be employed .pi.-type silencer 20b
such as shown in FIG. 4. In the .pi.-type silencer 20b, a
communication path 203b extends along the axis of the first
silencing space 201 from the inside of the first silencing space
201 and through the lower end of the first silencing space 201 to
the outside, and then penetrates the upper end of the second
silencing space 202 and extends into the inside of the second
silencing space 202. Additionally, in the .pi.-type silencer 20b,
an oil return hole 206 is disposed in the lower end portion of the
communication path 203b inside the first silencing space 201. When
the .pi.-type silencer 20b is employed, refrigerating machine oil
can be prevented from collecting in the .pi.-type silencer, and
just the communication path can be extended long without having to
change the size of the entire .pi.-type silencer. In a .pi.-type
silencer, the longer the communication path is, the larger the
pressure pulsation reduction effect becomes. In other words,
refrigerating machine oil can be prevented from collecting in the
.pi.-type silencer, and the pressure pulsation reduction effect can
be made larger without having to change the size of the entire
.pi.-type silencer.
(B)
[0089] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 where the
axes of the first silencing space 201, the second silencing space
202 and the communication path 203 are superposed on a straight
line and face the vertical direction, but instead of the .pi.-type
silencer 20, there may also be employed a .pi.-type silencer 20c
such as shown in FIG. 5. In the .pi.-type silencer 20c, a first
silencing space 201c and a second silencing space 202c are disposed
side-by-side, and the axes of both of the silencing spaces 201c and
202c are along the vertical direction but are not superposed on a
straight line. Additionally, in the .pi.-type silencer 20c, a
communication path 203c is U-shaped and extends from the lower end
of the first silencing space 201c to the lower end of the second
silencing space 202c. When the .pi.-type silencer 20c is employed,
the entire length of the .pi.-type silencer can be shortened.
Consequently, the options for the disposition of the .pi.-type
silencer in the outdoor unit 10 can be expanded.
[0090] Further, there may also be employed a .pi.-type silencer 20d
such as shown in FIG. 6. The .pi.-type silencer 20d is one where a
mesh member 207 fills the communication path 203c of the .pi.-type
silencer 20c shown in FIG. 5. When the .pi.-type silencer 20d is
employed, reflection waves can be prevented from arising inside the
communication path 203c.
[0091] Further, there may also be employed a .pi.-type silencer 20e
such as shown in FIG. 7. The .pi.-type silencer 20e is one where a
first refrigerant passage 204e and a second refrigerant passage
205e are inserted into the insides of the first silencing space
201c and the second silencing space 202c of the .pi.-type silencer
20c shown in FIG. 5. When the .pi.-type silencer 20e is employed,
it can be ensured that refrigerating machine oil does not collect
in the first silencing space 201c and the second silencing space
202c.
(C)
[0092] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 where the
axes of the first silencing space 201, the second silencing space
202 and the communication path 203 are superposed on a straight
line and face the vertical direction, but instead of the .pi.-type
silencer 20, there may also be employed a .pi.-type silencer 20f
such as shown in FIG. 8. In the .pi.-type silencer 20f, a first
silencing space 201c and a second silencing space 202c are disposed
side-by-side, and the axes of both of the silencing spaces 201c and
202c are along the vertical direction but are not superposed on a
straight line. Additionally, in the .pi.-type silencer 20f, a
communication path 203f is U-shaped, penetrates the upper end of
the first silencing space 201c from the inside of the first
silencing space 201c, extends to the upper end of the second
silencing space 202c, penetrates the upper end of the second
silencing space 202c and extends into the inside of the second
silencing space 202c. When the .pi.-type silencer 20f is employed,
the entire length of the .pi.-type silencer can be shortened,
refrigerating machine oil can be prevented from collecting in the
first silencing space 201c and the second silencing space 202c, and
just the communication path can be extended long without having to
change the size of the entire .pi.-type silencer. Consequently, the
options for the disposition of the .pi.-type silencer in the
outdoor unit 10 can be expanded, refrigerating machine oil can be
prevented from collecting in the first silencing space 201c and the
second silencing space 202c, and the pressure pulsation reduction
effect can be made larger without having to change the size of the
entire .pi.-type silencer.
(D)
[0093] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 where the
axes of the first silencing space 201, the second silencing space
202 and the communication path 203 are superposed on a straight
line and face the vertical direction, but instead of the .pi.-type
silencer 20, there may also be employed a .pi.-type silencer 20g
such as shown in FIG. 9. In the .pi.-type silencer 20g, a first
silencing space 201c and a second silencing space 202c are disposed
side-by-side, and the axes of both of the silencing spaces 201c and
202c are along the vertical direction but are not superposed on a
straight line. Additionally, in the .pi.-type silencer 20g, a
communication path 203g is S-shaped and extends from the lower end
of the first silencing space 201c to the upper end of the second
silencing space 202c. When the .pi.-type silencer 20g is employed,
refrigerating machine oil can be prevented from collecting in the
.pi.-type silencer, the entire length of the .pi.-type silencer can
be shortened, and the communication path can be made longer without
having to change the size of the entire .pi.-type silencer. In a
.pi.-type silencer, the longer the communication path is, the
larger the pressure pulsation reduction effect becomes. In other
words, refrigerating machine oil can be prevented from collecting
in the .pi.-type silencer, the options for the disposition of the
.pi.-type silencer in the outdoor unit 10 can be expanded, and the
pressure pulsation reduction effect can be made larger without
having to change the size of the entire .pi.-type silencer. It will
be noted that the communication path 203g that extends from the
lower end of the first silencing space 201c may also penetrate the
upper end of the second silencing space 202c and extend into the
inside of the second silencing space 202c.
(E)
[0094] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 where the
axes of the first silencing space 201, the second silencing space
202 and the communication path 203 are superposed on a straight
line and face the vertical direction, but instead of the .pi.-type
silencer 20, there may also be employed a .pi.-type silencer 20h
such as shown in FIG. 10. In the .pi.-type silencer 20h, a first
silencing space 201c and a second silencing space 202c are disposed
side-by-side, and the axes of both of the silencing spaces 201c and
202c are along the vertical direction but are not superposed on a
straight line. Additionally, in the .pi.-type silencer 20h, a first
refrigerant passage 204h is connected to the lower end of the first
silencing space 201c, and a second refrigerant passage 205h is
connected to the lower end of the second silencing space 202c.
Additionally, in the .pi.-type silencer 20h, a communication path
203c is U-shaped and extends from the lower end of the first
silencing space 201c to the lower end of the second silencing space
202c. When the .pi.-type silencer 20h is employed, refrigerating
machine oil can be prevented from collecting in the .pi.-type
silencer, and the entire length of the .pi.-type silencer can be
made shorter. Consequently, refrigerating machine oil can be
prevented from collecting in the .pi.-type silencer, and the
options for the disposition of the .pi.-type silencer in the
outdoor unit 10 can be expanded.
(F)
[0095] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 where the
axes of the first silencing space 201, the second silencing space
202 and the communication path 203 are superposed on a straight
line and face the vertical direction, but instead of the .pi.-type
silencer 20, there may also be employed a .pi.-type silencer 20i
such as shown in FIG. 11. The .pi.-type silencer 20i is housed in
the outdoor unit 10 such that axes of a first silencing space 201i
and a second silencing space 202i are superposed on a straight line
and face the horizontal direction. Additionally, in the .pi.-type
silencer 20i, a first refrigerant passage 204 is connected to the
lowermost portion of the outer end of the first silencing space
201i, and a second refrigerant passage 205 is connected to the
lowermost portion of the outer end of the second silencing space
202i. Additionally, in the .pi.-type silencer 20i, a communication
path 203i interconnects the lowermost portion of the inner end of
the first silencing space 201i and the lowermost portion of the
inner end of the second silencing space 202i. When the .pi.-type
silencer 20i is employed, refrigerating machine oil can be
prevented from collecting in the .pi.-type silencer.
[0096] Further, there may also be employed a .pi.-type silencer 20j
such as shown in FIG. 12. In the .pi.-type silencer 20j, a
communication path 203j penetrates the lowermost portion of the
inner end of the first silencing space 201i and the lowermost
portion of the inner end of the second silencing space 202i and
extends into the inside of the second silencing space 202i from the
inside of the first silencing space 201i. When the .pi.-type
silencer 20j is employed, refrigerating machine oil can be
prevented from collecting in the .pi.-type silencer, and the
communication path can be made longer without having to change the
size of the entire .pi.-type silencer. In a .pi.-type silencer, the
longer the communication path is, the larger the pressure pulsation
reduction effect becomes. In other words, refrigerating machine oil
can be prevented from collecting in the .pi.-type silencer, and the
pressure pulsation reduction effect can be made larger without
having to change the size of the entire .pi.-type silencer.
(G)
[0097] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 where the
axes of the first silencing space 201, the second silencing space
202 and the communication path 203 are superposed on a straight
line and face the vertical direction, but instead of the .pi.-type
silencer 20, there may also be employed a .pi.-type silencer 20k
such as shown in FIG. 13. The .pi.-type silencer 20k is housed in
the outdoor unit 10 such that axes of a first silencing space 201i,
a second silencing space 202i and a communication path 203k are
superposed on a straight line and face the horizontal direction.
Additionally, in the .pi.-type silencer 20k, a first oil drain
passage 206k extends from the lower end of the first silencing
space 201i, and a second oil drain passage 207k extends from the
lower end of the second silencing space 202i. It will be noted that
the first oil drain passage 206k and the second oil drain passage
207k merge midway and are connected to the suction pipe of the
compressor 11 via a capillary. When the .pi.-type silencer 20k is
employed, refrigerating machine oil can be prevented from
collecting in the .pi.-type silencer. It will be noted that the
communication path 203k may also penetrate the center of the inner
end of the first silencing space 201i and the center of the second
silencing space 202i and extend into the inside of the second
silencing space 202i from the inside of the first silencing space
201i.
(H)
[0098] In the air conditioner 1 pertaining to the preceding
embodiment, the .pi.-type silencer 20 was connected to the
discharge pipe of the compressor 11, but instead of this, the
.pi.-type silencer 20 may also be connected to the suction pipe of
the compressor 11. Further, the .pi.-type silencer 20 may also be
connected to both the discharge pipe and the suction pipe of the
compressor 11.
(I)
[0099] In the air conditioner 1 pertaining to the preceding
embodiment, although it was not touched upon, when vessels such as
an oil separator, an accumulator and a liquid receiver are present
in the refrigerant circuit 2, the spaces inside of those may also
be utilized as the first silencing space or the second silencing
space. By so doing, the refrigerant circuit 2 can be
simplified.
(J)
[0100] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed the .pi.-type silencer 20 in which
the two silencing spaces 201 and 202 are present, but instead of
this, there may also be employed a .pi.-type silencer where three
or more silencing spaces are present. By so doing, an even larger
pressure pulsation reduction effect can be expected.
(K)
[0101] In the air conditioner 1 pertaining to the preceding
embodiment, there was employed an inverter rotary type compressor,
but instead of this, there may also be employed a constant speed
rotary compressor.
(L)
[0102] In the air conditioner 1 pertaining to the preceding
embodiment, carbon dioxide was employed as the refrigerant, but
instead of this, a refrigerant such as R22 or R410A may also be
employed. Incidentally, when the pressure is 1.5 MPa, the density
becomes 56.4 kg/m.sup.3 and the speed of sound becomes 169 m/sec.
Further, when the pressure is 2.4 MPa, the density becomes 83.3
kg/m.sup.3 and the speed of sound becomes 174 msec.
(M)
[0103] In the .pi.-type silencer 20 pertaining to the preceding
embodiment, the shape of the first silencing space 201 was
cylindrical, but in the present invention, the shape of the first
silencing space 201 is not particularly limited and may also be a
cuboid or a regular hexahedron, for example.
(N)
[0104] In the .pi.-type silencer 20 pertaining to the preceding
embodiment, the shape of the second silencing space 202 was
cylindrical, but in the present invention, the shape of the second
silencing space 202 is not particularly limited and may also be a
cuboid or a regular hexahedron, for example.
[0105] (O)
[0106] In the .pi.-type silencer 20 pertaining to the preceding
embodiment, the first silencing space 201 and the second silencing
space 202 were configured to have the same shape and the same
volume, but in the present invention, the shapes and the volumes of
the first silencing space 201 and the second silencing space 202
may also be different.
(P)
[0107] In the .pi.-type silencer 20 pertaining to the preceding
embodiment, the shape of the communication path 203 was
cylindrical, but in the present invention, the shape of the
communication path 203 is not particularly limited and may also be
a cuboid, for example.
INDUSTRIAL APPLICABILITY
[0108] The refrigeration system pertaining to the present invention
has the characteristic that it can sufficiently reduce pressure
pulsation even when carbon dioxide is employed as a refrigerant, so
the refrigeration system is suited to a refrigeration system that
employs a supercritical refrigerant such as carbon dioxide as
refrigerant.
* * * * *