U.S. patent application number 13/000072 was filed with the patent office on 2011-05-05 for refrigerating cycle device and air conditioner.
This patent application is currently assigned to Mitsubishi Electric Corporation. Invention is credited to Toshihide Koda, Atsuhiro Yabu, Koji Yamashita.
Application Number | 20110100042 13/000072 |
Document ID | / |
Family ID | 41444389 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110100042 |
Kind Code |
A1 |
Yamashita; Koji ; et
al. |
May 5, 2011 |
REFRIGERATING CYCLE DEVICE AND AIR CONDITIONER
Abstract
A compressor for compressing a refrigerant containing a
substance having a double bond, a condenser for condensing the
refrigerant by heat exchange, expanding means for decompressing the
condensed refrigerant, and an evaporator for evaporating the
decompressed refrigerant by heat exchange are connected by piping
so as to configure a refrigerant circuit through which the
refrigerant is circulated, and control means is provided for
controlling an operation of the refrigerant circuit so that a
pressure of the refrigerant in the refrigerant circuit becomes less
than a critical pressure of the substance having the double
bond.
Inventors: |
Yamashita; Koji; (Tokyo,
JP) ; Yabu; Atsuhiro; (Tokyo, JP) ; Koda;
Toshihide; (Tokyo, JP) |
Assignee: |
Mitsubishi Electric
Corporation
Chiyoda-ku, Tokyo
JP
|
Family ID: |
41444389 |
Appl. No.: |
13/000072 |
Filed: |
June 12, 2009 |
PCT Filed: |
June 12, 2009 |
PCT NO: |
PCT/JP2009/060726 |
371 Date: |
December 20, 2010 |
Current U.S.
Class: |
62/228.1 ;
62/426; 62/498 |
Current CPC
Class: |
C09K 2205/126 20130101;
F25B 2400/121 20130101; F25B 2500/07 20130101; F25B 2313/02741
20130101; F25B 13/00 20130101; F25B 49/005 20130101; F25B 2700/191
20130101; F25B 2700/2116 20130101; F25B 9/002 20130101; F25B
2500/19 20130101; F25B 2600/111 20130101; F25B 2600/021 20130101;
C09K 5/045 20130101; F25B 2700/1931 20130101 |
Class at
Publication: |
62/228.1 ;
62/498; 62/426 |
International
Class: |
F25B 49/02 20060101
F25B049/02; F25B 1/00 20060101 F25B001/00; F25D 17/06 20060101
F25D017/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 24, 2008 |
JP |
2008-164454 |
Claims
1. A refrigerating cycle device, wherein a compressor for
compressing a refrigerant containing a substance having a double
bond; a condenser for condensing said refrigerant by heat exchange;
expanding means for decompressing the condensed refrigerant; and an
evaporator for evaporating said decompressed refrigerant by heat
exchange are connected by piping so as to constitute a refrigerant
circuit through which said refrigerant is circulated, and control
means is provided for controlling an operation of said refrigerant
circuit so that a pressure of said refrigerant in the refrigerant
circuit becomes less than a critical pressure of said substance
having the double bond to prevent said refrigerant from becoming a
supercritical state to destroy the double bond of said
refrigerant.
2. A refrigerating cycle device, wherein a compressor for
compressing a refrigerant containing a substance having a double
bond; a condenser for condensing said refrigerant by heat exchange;
expanding means for decompressing the condensed refrigerant; and an
evaporator for evaporating said decompressed refrigerant by heat
exchange are connected by piping so as to constitute a refrigerant
circuit through which said refrigerant is circulated, and control
means is provided for controlling operations of means constituting
said refrigerant circuit so that a value of a pressure of said
refrigerant in the refrigerant circuit becomes a pressure value or
less set on the basis of the lowest critical pressure in the
substance constituting said refrigerant.
3. The refrigerating cycle device of claim 1, further comprising
high-pressure side pressure detecting means disposed at a position
anywhere in a flow passage from an outlet side of said compressor
to an inlet of said expanding means and transmitting a signal on
the basis of a detected pressure, wherein said control means lowers
a compressor frequency of said compressor or stops said compressor
if said control means determines that the pressure value on the
basis of a signal of said high-pressure side pressure detecting
means is larger than a first pressure value.
4. The refrigerating cycle device of claim 1, further comprising
pressure storage means for storing values of a plurality of
pressures relating to detection of said high-pressure side pressure
detecting means for a predetermined period of time, wherein said
control means calculates a value of a pressure after the
predetermined time on the basis of the values of said plurality of
pressures as a forecast value, and if said control means judges
that said forecast value is larger than a second pressure value,
said control means controls operations of means constituting said
refrigerant circuit.
5. The refrigerating cycle device of claim 1, further comprising
blowing means for blowing air to be heat-exchanged with said
refrigerant to said condenser and/or said evaporator, wherein said
control means controls an operation of said blowing means.
6. The refrigerating cycle device of claim 1, wherein in the
refrigerating cycle device in which a plurality of said condensers
are connected in parallel, said control means controls operations
of means constituting said refrigerant circuit so as to lower a
pressure of the refrigerant in said refrigerant circuit before
refrigerant supply to at least one of said condensers is stopped or
substantially at the same time as the stop.
7. The refrigerating cycle device of claim 6, wherein said control
means lowers a compressor frequency in said compressor so as to
lower the refrigerant pressure in said refrigerant circuit.
8. The refrigerating cycle device of claim 1, wherein in the
refrigerating cycle device in which a plurality of flow-rate
control means including said expanding means for adjusting a flow
rate of said refrigerant in said refrigerant circuit is disposed in
said refrigerant circuit, said control means executes control such
that at least one of the flow-rate control means is opened if a
space between at least two flow-rate control means is judged to be
in a sealed state.
9. The refrigerating cycle device of claim 8, wherein pressure
detecting means for transmitting a signal on the basis of a
detected pressure is disposed between said plurality of flow-rate
control means; and said control means judges a sealed state of said
piping on the basis of the signal from the pressure detecting means
between said flow-rate control means.
10. The refrigerating cycle device of claim 8, wherein said control
means executes control to open at least either of said flow-rate
control means after a predetermined time has elapsed since the
judgment of said sealed state.
11. An air conditioner, wherein cooling/heating for a target space
is performed by the refrigerating cycle device of claim 1.
12. The refrigerating cycle device of claim 2, further comprising
high-pressure side pressure detecting means disposed at a position
anywhere in a flow passage from an outlet side of said compressor
to an inlet of said expanding means and transmitting a signal on
the basis of a detected pressure, wherein said control means lowers
a compressor frequency of said compressor or stops said compressor
if said control means determines that the pressure value on the
basis of a signal of said high-pressure side pressure detecting
means is larger than a first pressure value.
13. The refrigerating cycle device of claims 2, further comprising
pressure storage means for storing values of a plurality of
pressures relating to detection of said high-pressure side pressure
detecting means for a predetermined period of time, wherein said
control means calculates a value of a pressure after the
predetermined time on the basis of the values of said plurality of
pressures as a forecast value, and if said control means judges
that said forecast value is larger than a second pressure value,
said control means controls operations of means constituting said
refrigerant circuit.
14. The refrigerating cycle device of claim 2, further comprising
blowing means for blowing air to be heat-exchanged with said
refrigerant to said condenser and/or said evaporator, wherein said
control means controls an operation of said blowing means.
15. The refrigerating cycle device of claim 2, wherein in the
refrigerating cycle device in which a plurality of said condensers
are connected in parallel, said control means controls operations
of means constituting said refrigerant circuit so as to lower a
pressure of the refrigerant in said refrigerant circuit before
refrigerant supply to at least one of said condensers is stopped or
substantially at the same time as the stop.
16. The refrigerating cycle device of claim 15, wherein said
control means lowers a compressor frequency in said compressor so
as to lower the refrigerant pressure in said refrigerant
circuit.
17. The refrigerating cycle device of claim 2, wherein in the
refrigerating cycle device in which a plurality of flow-rate
control means including said expanding means for adjusting a flow
rate of said refrigerant in said refrigerant circuit is disposed in
said refrigerant circuit, said control means executes control such
that at least one of the flow-rate control means is opened if a
space between at least two flow-rate control means is judged to be
in a sealed state.
18. The refrigerating cycle device of claim 17, wherein pressure
detecting means for transmitting a signal on the basis of a
detected pressure is disposed between said plurality of flow-rate
control means; and said control means judges a sealed state of said
piping on the basis of the signal from the pressure detecting means
between said flow-rate control means.
19. The refrigerating cycle device of claim 17, wherein said
control means executes control to open at least either of said
flow-rate control means after a predetermined time has elapsed
since the judgment of said sealed state.
20. An air conditioner, wherein cooling/heating for a target space
is performed by the refrigerating cycle device of claim 2.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigerating cycle
device constituting a refrigerating cycle such as air conditioners
including a multi-air conditioner for building, a room-air
conditioner, a package air conditioner and the like, a refrigerator
and the like.
BACKGROUND ART
[0002] In a refrigerating cycle device using a refrigerating cycle
(heat-pump cycle) such as an air conditioner, a freezer, a water
heater and the like, basically, a compressor, a condenser (heat
exchanger), an expansion valve, and an evaporator (heat exchanger)
are connected by piping so as to constitute a refrigerant circuit
through which a refrigerant is circulated, for example. By using
heating (radiation) and cooling (heat absorption) of a
heat-exchange target by the refrigerant in evaporation and
condensation, an air-conditioning operation, a cooling operation, a
heating operation and the like are performed while a pressure
inside a pipe is changed.
[0003] Here, as refrigerant in a refrigerant circuit in a prior-art
refrigerating cycle device, single refrigerant such as HCFC-22
(CHClF.sub.2) and HFC-134a (CF.sub.3CH.sub.2F) and mixed
refrigerant such as R-410A, which is a mixture of HFC-32
(CH.sub.2F.sub.2) and HFC-125 (CH.sub.3CHF.sub.2), and R-407C,
which is a mixture of HFC-32 (CH.sub.2F.sub.2) and HFC-425
(CF.sub.3CF.sub.2), and HFC-134a (CF.sub.3CH.sub.2F), which are
chemically stable substances, are used (See Patent Literature 1,
for example)
CITATION LIST Patent Literature
PTL 1: Japanese Unexamined Patent Application Publication No.
2006-152839 (Claim 2)
SUMMARY OF INVENTION
Technical Problem
[0004] Here, as a refrigerant circulating through a refrigerant
circuit, from a viewpoint of preventing global warming, a
refrigerant having as small global warming coefficient (GWP: a
degree of incurring global warming with respect to a substance,
which is a greenhouse effect gas, represented by a coefficient
determined on the basis of knowledge internationally approved as
numeral values indicating a ratio to the degree regarding carbon
dioxide) as possible is preferably used Such refrigerant includes
those containing a substance having a double bond (multi bond) in
an atomic bond such as CF.sub.3CF.dbd.CH.sub.2,
CF.sub.3CH.dbd.CH.sub.2, CF.sub.3CF.dbd.CF.sub.2 and the like
(hereinafter referred to as refrigerant having a double bond).
[0005] Since in the prior-art refrigerating cycle device, a
chemically stable substance is used as a refrigerant, there is no
need to worry that the substance in the refrigerant might be
decomposed during use (hereinafter referred to as decomposition of
a refrigerant) or the like and stop functioning as a refrigerant.
However, since the refrigerant having the double bond as above is a
chemically unstable refrigerant, it is likely that the refrigerant
might be decomposed and deteriorated under a usual method of use.
For example, in the case of the mixed refrigerant, too, the mixed
refrigerant as a whole might stop functioning since it is
decomposed and deteriorated by the other refrigerants or decomposes
and deteriorates the other refrigerants, and as a result, there is
a possibility that the refrigerating cycle device cannot be used
normally.
[0006] The present invention was made in order to solve the above
problems and has an object to obtain a refrigerating cycle device
or the like that can prevent decomposition of the refrigerant and
maintain a normal operation for a long time even if a refrigerant
containing a chemically unstable substance such as a refrigerant
having a double bond is used as a refrigerant to be circulated
through a refrigerant circuit.
Solution To Problem
[0007] In a refrigerating cycle device according to the present
invention, a refrigerant circuit is configured by connecting a
compressor for compressing a refrigerant containing a substance
having a double bond, a condenser for condensing the refrigerant by
heat exchange, expanding means for decompressing the condensed
refrigerant, and an evaporator for evaporating the decompressed
refrigerant by heat exchange by piping and the device is provided
with control means for controlling an operation of the refrigerant
circuit so that a pressure value of the refrigerant in the
refrigerant circuit becomes less than a critical pressure of the
substance having the double bond.
Advantageous Effects of Invention
[0008] According to the refrigerating cycle device of the present
invention, in configuring a refrigerant circuit through which a
refrigerant containing a substance having double bond is
circulated, since an operation of the refrigerant circuit is
controlled so that a pressure value of the refrigerant in the
refrigerant circuit becomes less than a critical pressure of the
substance having double bond, in the refrigerant containing the
substance having chemically unstable double bond, decomposition of
the substance itself having double bond due to exceeding of the
critical pressure by the substance having double bond or attack on
the substance having double bond due to exceeding of the critical
pressure of the other substances, which results in non-functioning
as the refrigerant, can be effectively suppressed. Therefore,
performances of the refrigerating cycle device can be maintained
for a long time, and moreover, reliability can be ensured. As a
result, a refrigerating cycle device can be obtained in which a
refrigerant with a smaller global warming coefficient and
containing a substance suitable for the environment and having
double bond, for example, can be effectively used.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a diagram illustrating a configuration of a
refrigerating cycle device according to Embodiment 1 of the present
invention.
[0010] FIG. 2 is a P-h diagram of the refrigerating cycle device
according to Embodiment 1 of the present invention.
[0011] FIG. 3 is a diagram illustrating a chemical change of
refrigerant having double bond.
[0012] FIG. 4 is a diagram illustrating a configuration including a
system according to control of Embodiment 1.
[0013] FIG. 5 is a diagram illustrating a flowchart of the
refrigerating cycle device according to Embodiment 1.
[0014] FIG. 6 is a diagram illustrating a configuration of an air
conditioner according to Embodiment 2 of the present invention.
[0015] FIG. 7 is a diagram illustrating a configuration of an air
conditioner according to Embodiment 3 of the present invention.
DESCRIPTION OF EMBODIMENTS
Embodiment 1
[0016] FIG. 1 is a diagram illustrating a configuration of a
refrigerating cycle device according to Embodiment 1 of the present
invention. In FIG. 1, the refrigerating cycle device has a
compressor 21, a condenser 22, a condenser fan 31, expanding means
23, an evaporator 24, an evaporator fan 32, and pressure detecting
means 41. A refrigerant circuit is configured by connecting the
compressor 21, the condenser 22, the expanding means 23, and the
evaporator 24 by piping. Here, in this Embodiment, a mixed
refrigerant in which at least one type of refrigerant containing a
substance having double bond in atomic bond is mixed is sealed as a
refrigerant to become a medium for carrying heat in the refrigerant
circuit. The refrigerant will be described later.
[0017] The compressor 21 sucks the refrigerant to be circulated in
the refrigerant circuit, compresses it and raises its pressure. For
the compressor 21, any of various types such as reciprocating,
rotary, scroll, screw and the like may be used. Also, the
compressor may be provided with an inverter circuit, for example,
that can change a capacity (an amount of the refrigerant to be fed
per unit time) by arbitrarily changing a compressor frequency even
in a compressor with a fixed compressor frequency. The condenser 22
performs heat exchange between a gas state refrigerant (hereinafter
referred to as a gas refrigerant) discharged by the compressor 21
and a heat-exchange target (supposing to be air in this
Embodiment), emits a heat quantity of the refrigerant to heat the
air. The condenser fan 31 feeds air to the condenser 22 so as to
perform heat exchange with the refrigerant efficiently. The
expanding means 23 is constituted by an electronic expansion valve,
a temperature-type expansion vale, a capillary tube and the like
and adjusts a flow rate of the passing refrigerant to lower the
pressure of the refrigerant (to decompress).
[0018] The evaporator 24 performs heat exchange between a
gas-liquid two-phase refrigerant (a refrigerant in a state in which
a gas refrigerant and a liquid-state refrigerant (hereinafter
referred to as a liquid refrigerant) are mixed) whose pressure is
lowered by the expanding means 23 and the heat-exchange target
(supposing to be air, too) so that the refrigerant absorbs the heat
quantity and is gasified. The air is cooled. The evaporator fan 32
is also provided for efficient heat exchange between the air and
the refrigerant in the evaporator 24. Here, the heat exchange with
air is performed using the condenser fan 31 and the evaporator fan
32, but heat exchange with water can be performed using a water
cooler using a pump and water instead of the condenser fan 23, a
device such as a chiller using pump and water or brine instead of
the evaporator fan 26 and the like.
[0019] The pressure detecting means 41, which is a pressure sensor,
is disposed on the side of a refrigerant outlet (discharge) of the
compressor 21, which is a portion with the highest pressure in the
refrigerant circuit in this Embodiment and transmits a signal on
the basis of a pressure relating to the detection to control means
or the like, which will be described later. Here, a level of the
pressure in the refrigerant circuit is not determined by a
relationship with a pressure to be a reference but is indicated as
a relative pressure determined by compression of the compressor 21,
refrigerant flow-rate control of the expanding means 23 and the
like. The same applies to a degree of the temperature.
[0020] In FIG. 1, a configuration with a single unit of the
condenser 22 and a single unit of the evaporator 24 is described as
an example, but the number of connection of the condenser 22 and
the evaporator 24 in the refrigerant circuit is not limited to one,
but a plurality of units can be connected in parallel, for example.
In the case of the compressor 21, a configuration with a single
unit is also described as an example, but a plurality of
compressors 21 can be connected in series or in parallel, for
example.
[0021] FIG. 2 is a P-h diagram relating to the refrigerant circuit
configured by the refrigerating cycle device in FIG. 1. Pressures
and enthalpy at points a, b, c, and d shown in FIG. 2 represent the
pressures and enthalpy at the corresponding points in the
refrigerating cycle device in FIG. 1.
[0022] Subsequently, an operation of the refrigerating cycle device
according to this Embodiment will be described on the basis of a
flow of a refrigerant. The high-temperature refrigerant having been
compressed by the compressor 21 and to become a pressure Pa on the
outlet (discharge) side is fed into the condenser 22 through the
piping. The refrigerant having passed through the condenser 22 is
condensed and liquefied by heat exchange with air fed in by the
condenser fan 31. At this time, the refrigerant emits heat, by
which the heat-exchange target is heated. Due to pressure loss
generated during this process, the pressure of the refrigerant is
slightly lowered from Pa to Pb.
[0023] The liquefied refrigerant is fed into the expanding means
23. The liquid refrigerant is decompressed while passing through
the expanding means 23 so as to become the gas-liquid two-phase
refrigerant and is fed into the evaporator 24. The gas-liquid
two-phase refrigerant having passed through the evaporator 24 is
heat-exchanged with the air fed in by the evaporator fan 32 and
evaporated and gasified. The gasified refrigerant is sucked again
by the compressor 21.
[0024] At this time, in the refrigerant circuit, a flow passage of
the refrigerant from the compressor 21 to the expanding means 23 is
a high-pressure flow passage, which is a flow passage with a
relatively high pressure in the refrigerant circuit. In general,
the pressure Pa of the refrigerant on the outlet side of the
compressor 21 is the highest, while the pressure Pb of the
refrigerant on the inlet side of the expanding means 23 is slightly
lower than Pa due to the pressure loss in the condenser 22 and the
connection piping. In each of Embodiments including this
Embodiment, control for keeping the refrigerant pressure in the
refrigerant circuit low is performed by constituent means of the
refrigerating cycle device, but the refrigerant pressure here is
basically supposed to the pressure Pa of the refrigerant on the
outlet side of the compressor 21.
[0025] In the P-h diagram shown in FIG. 2, a point where a
saturated liquid line meets a saturated gas line is referred to as
a critical point, and in a state in which the refrigerant pressure
is higher than a pressure at the critical point (hereinafter
referred to as a critical pressure. It is a pressure Pcr in FIG.
2), the refrigerant is in a supercritical state, which is neither
liquid nor gas. If the refrigerant is brought into the
supercritical state, it presents a nature different from that in
the gas state or liquid state. In the supercritical state, even a
substance, which is stable in a usual use, has a nature to
decompose, a nature that dissolves various substances well and the
like are shown. Such high solubility and reactivity require
consideration for materials of a container or a seal in the
compressor 21 or the like.
[0026] Here, a mixed refrigerant constituted as a mixture of a
plurality of types of refrigerants is considered. Mixed
refrigerants usually used include R-410A, which is a mixture of
HFC-32 and HFC-125, R-407C, which is a mixture of HFC-32, HFC-125,
and HFC-134a and the like.
[0027] Expressing substances constituting the respective
refrigerants by chemical formulas, HFC-32 is CH.sub.2F.sub.2,
HFC-125 is CH.sub.3CHF.sub.2, and HFC-134a is CF.sub.3CH.sub.2F.
These refrigerants are chemically stable and remain as global
warming gases for a long time. Thus, values of their global warming
coefficients indicating a rate to contribute to the global warming
are relatively large.
[0028] On the other hand, in an atomic bond constituting a
substance, a refrigerant made of a substance having a double bond
might be mixed with other refrigerants. The refrigerant made of a
substance having the double bond includes CF.sub.3CF.dbd.CH.sub.2
(hydrofluoroolefin (HFO) refrigerant represented by
2,3,3,3-tetrafluoropropene and HFO-1234yf) and a refrigerant
containing substances such as CF.sub.3CH.dbd.CH.sub.2,
CF.sub.3CF.dbd.CF.sub.2 and the like (the symbol ".dbd." represents
a double bond), for example. From a viewpoint of the global
environment, a mixed refrigerant in which a plurality of types of
refrigerants with smaller global warming coefficients and made of
substances having the double bond are mixed may be preferably used,
but a refrigerant made of a substance bonded by a single bond such
as HFC-32, HFC-125, HFC-134a and the like or other refrigerants can
be also mixed.
[0029] Here, the substance having double bond has a chemically
unstable nature, and the refrigerant made of such substance has a
nature of being easily decomposed in the air, for example, due to
an influence of light, ozone and the like. Thus, since they do not
remain as a global warming gas for a long time, they have a little
influence on the warming and their values of global warming
coefficient are relatively small. Also, not only in the air, if the
single refrigerant made of a substance having double bond or a
mixed refrigerant containing the refrigerant made of a substance
having double bond (refrigerant having double bond) is sealed to be
used as a refrigerant to be circulated through the refrigerant
circuit (working fluid), the double bond is decomposed in the
refrigerant circuit, and there is a risk that the refrigerant stops
functioning as refrigerant.
[0030] FIG. 3 is a diagram illustrating an example of decomposition
of CF.sub.3CF.dbd.CH.sub.2 or the like. Here, the decomposition of
double bond will be described using the decomposition of
CF.sub.3CF.dbd.Cl.sub.2 as an example. For example,
CF.sub.3CF.dbd.CH.sub.2 causes a chemical change as shown in FIG.
3. Molecules of CF.sub.3CF.dbd.CH.sub.2 might be polymerized to
become a polymer compound with a large molecular weight in the form
of CF.sub.3CFCH.sub.2 (CF.sub.3CFCH.sub.2)nH. This polymer compound
becomes a sludge and circulates with the refrigerant in the
refrigerant circuit, which causes valve clogging or the like in the
expanding means or the like whose flow passage is narrow, for
example. If water is present in the refrigerant circuit, the
compound might become alcohol presenting acidity in the form of
CF.sub.3CFCOHCH.sub.3 or sludge. Moisture in the refrigerant
circuit is usually adsorbed and removed by a drier (not shown) or
the like. Moreover, the polymer might become an acid in the form of
CH.sub.3CFHC.dbd.OOH and change its property and in the end, stop
performing a function as a refrigerant.
[0031] Therefore, if the refrigerant having double bond is used as
a refrigerant to be circulated in the refrigerant circuit (working
fluid), it should be used in a state in which a cause to promote
decomposition of the refrigerant such as air, light and the like is
removed as much as possible.
[0032] Here, the mixed refrigerant will be described. The mixed
refrigerant has different natures relating to heat, different
refrigerating cycles (P-h diagram), and different critical points
depending on constituting refrigerants. In the refrigerating cycle
device using the mixed refrigerant as the refrigerant circulating
in the refrigerant circuit (working fluid), each refrigerant
repeats condensation and evaporation and circulates in the
refrigerant circuit. Here, among refrigerants constituting the
mixed refrigerant, a critical pressure of the refrigerant with the
lowest critical point is referred to as the lowest critical
pressure.
[0033] The critical pressure of the refrigerant is 5.78 MPa for
HFC-32, 3.616 MPa for HFC-125, 4.048 MPa for HFC-134, and
approximately 3.3 MPa for CF.sub.3CF.dbd.CH.sub.2, for example.
Therefore, if the refrigerants of HFC-32, HFC-125, and
CF.sub.3CF.dbd.CH.sub.2 are mixed, the critical pressure of
CF.sub.3CF.dbd.CH.sub.2 is the smallest, and
CF.sub.3CF.dbd.CH.sub.2 itself is the first to be brought into the
supercritical state.
[0034] Here, in the refrigerant circuit through which the mixed
refrigerant is circulated, if the pressure of the refrigerant
(particularly, the pressure on the high-pressure side) is lower
than the lowest critical pressure all the time, the refrigerants
are not decomposed or the like but circulated in the refrigerant
circuit for a long time and is capable of repeated condensation,
evaporation and the like. However, if the refrigerant pressure
becomes higher than the lowest critical pressure, the refrigerant
with a low critical pressure is brought into the supercritical
state, and it is circulated in the supercritical state with other
refrigerants in the refrigerant circuit.
[0035] If the refrigerant is brought into the supercritical state,
as mentioned above, even a substance which is usually stable will
have a nature to decompose another substance or the like. Thus, in
the mixed refrigerant, if the refrigerant in the supercritical
state exceeding the critical pressure is present, it would attack
and try to decompose the other refrigerants.
[0036] In the mixed refrigerant constituted only by chemically
stable refrigerants such as R-410A and R-407C, for example, even if
the refrigerant pressure on the high pressure side becomes higher
than the lowest critical pressure and a part of the refrigerants is
brought into the supercritical state, the mixed refrigerant as a
whole is not decomposed but can be used stably.
[0037] When the refrigerant made up of a substance having double
bond such as CF.sub.3CF.dbd.CH.sub.2 is contained in the mixed
refrigerant, if refrigerants other than the refrigerant made up of
the substance having double bond is brought into the supercritical
state, for example, the refrigerant in the supercritical state
attacks the refrigerant made up of the chemically unstable
substance having double bond, and the refrigerant is decomposed and
cannot maintain stable properties any longer. Also, if all the
refrigerants are decomposed or the like, the mixed refrigerant will
not function as a refrigerant at all.
[0038] Thus, in the mixed refrigerant containing the refrigerant
made up of a substance having double bond, it is indispensable that
the refrigerant pressure at all the positions in the refrigerant
circuit is controlled so that the pressure is at the lowest
critical pressure or less all the time and the mixed refrigerant is
circulated so that none of the refrigerants is brought into the
supercritical state.
[0039] Also, the refrigerant in the supercritical state also
attacks itself. Thus, the above also applies to a situation in
which the critical pressure of the other refrigerants are higher
than the refrigerant made up of a substance having the double bond
or a situation in which only the refrigerant made up of a substance
having the double bond is used as a refrigerant, and if the device
is to be operated, control should be made in circulating the
refrigerant so that the refrigerant is not turned into the
supercritical state.
[0040] As mentioned above, a flow passage to become the high
pressure side in the refrigerant circuit is a flow passage leading
from the compressor 21 to the expanding means 23. In this flow
passage, too, since the refrigerant is compressed and boosted in
the compressor 21, in the general refrigerating cycle device, the
pressure on the outlet (discharge) side of the compressor 21 is the
highest in the refrigerant circuit.
[0041] Then, in this Embodiment, the pressure detecting means 41 is
disposed on the outlet side of the compressor 21 so as to obtain
the refrigerating cycle device controlled so that a pressure on the
basis of a signal from the pressure detecting means 41 does not
exceed the lowest critical pressure.
[0042] FIG. 4 is a diagram illustrating a configuration of the
refrigerating cycle device including a system relating to control
of this Embodiment. In FIG. 4, control means 53 executes processing
for controlling operations of each means of the refrigerating cycle
device. Particularly in this Embodiment, the control means
functions as high-pressure control means for controlling each means
by determining a value of a refrigerant pressure of a portion to
become the highest pressure in the refrigerant circuit (hereinafter
referred to as a high-pressure pressure value) on the basis of a
signal from the pressure detecting means 41 and executing
processing such as calculation. Pressure storage means 51 stores
data of a plurality of high-pressure pressure values per
predetermined interval for a past predetermined period of time.
Also, the critical pressure storage means 52 is means for storing a
pressure value set on the basis of the lowest critical pressure
mentioned in the mixed refrigerant. Here, the means stores two
values, that is, a first pressure value and a second pressure
value.
[0043] FIG. 5 is a diagram illustrating a flowchart of pressure
control executed by the control means 53. On the basis of FIGS. 4
and 5, an operation of the refrigerating cycle device in this
Embodiment mainly on the processing executed by the control means
53 will be described. On the basis of a signal transmitted from the
pressure detecting means 41 installed on the outlet side of the
compressor 21, the control means 53 determines a high-pressure
pressure value (ST1) and has it stored in the pressure storage
means 51.
[0044] Also, the control means 53 compares the high-pressure
pressure value with the first pressure value stored in the critical
pressure storage means 52 (ST2). Here, in this Embodiment, with
regard to the first pressure value, a value obtained by subtracting
a predetermined value a to become a margin from a value of the
lowest critical pressure is set as the first pressure value so that
it becomes less than the critical pressure having double bond, for
example, considering a detection error of pressure contained in the
high-pressure pressure value, a refrigerant pressure inside the
compressor 21 and the like. The first pressure value is a value
lower than the lowest critical pressure. A value of the
predetermined value a can be determined arbitrarily but here, it is
supposed to be 0.2 (MPa).
[0045] As the result of comparison, if it is determined that the
high-pressure pressure value is larger than the first pressure
value, the control means 53 controls the compressor 21 so as to
rapidly lower the refrigerant pressure on the high pressure side of
the refrigerant circuit (ST3) so that the refrigerant is not
decomposed. The control of the compressor 21 includes rapid
lowering of a compressor frequency if the compressor 21 is a
compressor having an inverter circuit, for example. Alternatively,
if the compressor 21 is a compressor with a fixed compressor
frequency, its operation is temporarily stopped.
[0046] On the other hand, as the result of comparison, if it is
determined that the high-pressure pressure value is not more than
the first pressure value, then, on the basis of data of the
plurality of high-pressure pressure values for a past predetermined
period of time stored in the pressure storage means 51, a forecast
value of a pressure after a predetermined time is calculated (ST4).
Regarding calculating the forecast value, a variation with time
(trend) is derived from a plurality of high-pressure pressure
values using a method as a three-point forecast method or the like,
and a pressure value after a predetermined time is calculated as a
forecast value. Here, the control means 53 may calculate the
forecast value not only by the three-point forecast method but also
by other methods.
[0047] The control means 53 compares the calculated forecast value
and the second pressure value stored in the critical pressure
storage means 52 (ST5). Here, with the second pressure value, too,
a value obtained by subtracting a predetermined value .beta. to
become a margin from a value of the lowest critical pressure is set
as the second pressure value, considering a detection error of a
pressure included in the high-pressure pressure value or the like.
The second pressure value is also a value lower than the lowest
critical pressure. A value of the predetermined value .beta. can be
determined arbitrarily, but it is supposed to be 0.5 (MPa), here.
Here, the first pressure value is made different from the second
pressure value, but they may be the same. Alternatively, only one
of comparison between the high-pressure pressure value and the
first pressure value and comparison between the forecast value and
the second pressure value can be made.
[0048] As the result of comparison, if it is determined that the
high-pressure pressure value is larger than the second pressure
value, the control means 53 controls operations of one or more
means of the compressor 21, the condenser fan 31, the evaporator
fan 32, and the expanding means 23 of the refrigerating cycle
device. By means of this control, the refrigerant pressure on the
high-pressure side of the refrigerant circuit is lowered so that
the pressure does not exceed the lowest critical pressure and the
refrigerant is not decomposed. Here, in the control to lower the
refrigerant pressure executed by the control means 53, if the
compressor 21 is a compressor having an inverter circuit, for
example, the compressor frequency is lowered by a predetermined
amount (10 Hz, for example). Also, with regard to the condenser fan
31, a heat quantity of the refrigerant in the condenser 22 is
emitted by increasing the rotation number of the fan. Also, with
regard to the expanding means 23, an opening degree is increased
and the pressure on the high pressure side is lowered. With regard
to the evaporator fan 32, the rotation number of the fan is
decreased, and absorption of the heat quantity by the refrigerant
in the evaporator 24 is suppressed. The control means 53 repeats
the above processing and controls each means of the refrigerating
cycle device so that even one type of the refrigerants constituting
the mixed refrigerant circulating in the refrigerant circuit is not
decomposed or the like.
[0049] Here, in this Embodiment, a configuration in which the
pressure detecting means 41 is installed at an outlet portion of
the compressor 21 was described as an example, but the installation
position is not limited to the outlet portion. Pressure loss from
the outlet of the compressor 21 to the condenser 22 or the
expanding means 23 can be calculated from a piping diameter, a
piping length, a refrigerant flow-rate and the like, for example.
By installing the pressure detecting means 41 at the inlet side of
the condenser 22 or the inlet side of the expanding means 23, for
example, a pressure at the outlet of the compressor 21 can be
estimated and calculated easily from a refrigerant pressure value
relating to detection at the position. Thus, only if the pressure
detecting means 41 is installed at a position anywhere from the
compressor outlet to the expanding means inlet, control can be made
so that the pressure on the compressor outlet side does not exceed
the lowest critical pressure.
[0050] Also, regarding the pressure detecting means 41, a pressure
sensor of a semiconductor type or a strain gauge type for
performing signal transmission according to a detected pressure is
generally used. However, the pressure detecting means 41 is not
limited to these types of pressure sensor but a pressure sensor
outputting an ON signal at a predetermined pressure may be used,
for example. In this case, the control means 53 does not have to
determine the high-pressure pressure value.
[0051] Also, if a pressure switch is used, a value slightly lower
than the lowest critical pressure is set as a predetermined
pressure in the pressure switch, and wiring is laid so that a
compression operation of the compressor 21 is stopped by an ON
signal outputted by the pressure switch at the predetermined
pressure. In this case, the pressure storage means 51, the critical
pressure storage means 52, and the control means 53 as
high-pressure control means in this Embodiment are not necessary
any more, and an inexpensive control system can be configured.
However, the compressor 21 repeats start and stop in the vicinity
of the lowest critical pressure. Thus, there is a possibility that
cooling capacity or heating capacity cannot be fully exerted, and
the pressure sensor is preferably used.
[0052] Also, temperature detecting means such as a temperature
sensor or the like for detecting a condensation temperature may be
installed close to the center of the condenser 22 instead of the
pressure detecting means 41, for example, so that a refrigerant
pressure on the high pressure side is calculated on the basis of a
condensation temperature. In order to detect the condensation
temperature, the refrigerant needs to be in a gas-liquid two-phase
state at a position where the temperature detecting means is
installed, basically, and if the means are installed at plural
locations, detection accuracy of the condensation temperature can
be improved, by which detection accuracy of the pressure can be
also improved.
[0053] As mentioned above, according to the refrigerating cycle
device of Embodiment 1, if a refrigerant circuit through which a
refrigerant containing a substance having double bond such as
CF.sub.3CF.dbd.CH.sub.2, CF.sub.3CH.dbd.CH.sub.2,
CF.sub.3CF.dbd.CF.sub.2 and the like is circulated is to be
configured, if the control means 53 determines that a pressure on
the outlet side of the compressor 21 to become the highest pressure
portion in the refrigerant circuit is larger than the first
pressure value set on the basis of the lowest critical pressure,
which is the lowest in the substances constituting the refrigerant,
control is made so that the compressor frequency of the compressor
21 is rapidly lowered or the compressor 21 is stopped so as to
prevent the lowest critical pressure from being exceeded. Thus, the
refrigerant containing a chemically unstable substance having
double bond can be prevented from being attacked by decomposition
of the substance itself having double bond or decomposition of
substances of the other refrigerants in the mixed refrigerant and
decomposed so as to stop functioning as a refrigerant. Therefore,
performances of the refrigerating cycle device can be maintained
for a long time, and reliability can be also ensured. Here, the
pressure can be lowered by other means, but in order to lower the
pressure on the outlet side of the compressor 21, it is most
effective to rapidly lower the compressor frequency of the
compressor 21 or to stop the compressor 21. Also, since
deterioration of the refrigerant is prevented and heat-quantity
feeding, which is a role of the refrigerant, can be maintained
without giving a load to the compressor 21, energy can be saved.
Also, the HFO refrigerant such as tetrafluoropropylene or the like
used as refrigerant at this time has a global warming coefficient
equivalent to that of carbon dioxide, which is a natural
refrigerant, for example, and this is preferable in terms of the
environment.
[0054] Also, since the forecast value of the refrigerant pressure
on the outlet side of the compressor 21 after a predetermined time
is calculated by a three-point forecast method or the like, for
example, on the basis of data of the high-pressure pressure value
for a past predetermined period of time relating to detection of
the pressure detecting means 41 and if the value is determined to
be larger than the second pressure value, the refrigerant pressure
is lowered by control, a trend of the refrigerant pressure can be
determined so that the trend is responded according to the
determination and the pressure does not exceed the lowest critical
pressure, and the refrigerant can be prevented from being
decomposed. Also, by controlling one or more in combination of the
condenser fan 31, the evaporation fan 32 and the like, the
refrigerant pressure on the outlet side of the compressor 21 can be
effectively lowered.
Embodiment 2
[0055] FIG. 6 is a diagram illustrating a configuration of an air
conditioner according to Embodiment 2 of the present invention. In
this Embodiment, an air conditioner such as a multi air conditioner
for building will be described as a typical example of the
refrigerating cycle device in Embodiment 1. In FIG. 6, means and
the like given the same reference numerals as those in FIG. 1 are
means basically performing the same operations as the operations
described above. Here, the control means 53 in this Embodiment
executes control for controlling operations of each means
(particularly means on the side of an outdoor unit 60) of the
refrigerating cycle device on the basis of an operation state of
indoor units 61a and 61b.
[0056] The air conditioner in FIG. 6 has the single outdoor unit 60
and two indoor units 61a and 61b. The outdoor unit 60 has the
compressor 21, an outdoor heat exchanger 25, a four-way valve 27,
an accumulator 28, an outdoor heat exchanger fan 33, and the
pressure detecting means 41. Also, the indoor units 61a and 61b
have expanding means 23a and 23b, indoor heat exchangers 26a and
26b, and indoor heat exchanger fans 34a and 34b, respectively. If
not particularly being distinguished, the indoor units 61a and 61b
and their constituting means will be described with omitting their
suffixes (the same applies to the following).
[0057] The outdoor heat exchanger 25 functions as the condenser 22
in Embodiment 1 in a cooling operation, into which a refrigerant
discharged by the compressor 21 flows, and functions as the
evaporator 24 in a heating operation by switching of the four-way
valve 27 and performs heat exchange between air and the
refrigerant. Also, the indoor heat exchangers 26a and 26b function
as the evaporator 24 in a cooling operation, contrary to the
outdoor heat exchanger 25, and function as the condenser 22 in a
heating operation and perform heat exchange between indoor air of a
space to be air-conditioned and the refrigerant.
[0058] Also, the accumulator 28 is means for reserving extra
refrigerant. Here, a case in which the accumulator is attached to
the intake side of the compressor 21 is shown, but a receiver may
be attached to the outlet side of the heat exchanger to become the
condenser 22, for example, so that the liquid refrigerant is
reserved. The outdoor heat exchanger fan 33, the indoor heat
exchanger fans 34a and 34b are provided for efficient heat exchange
between the air and the refrigerant. In the air conditioner in this
Embodiment, too, the refrigerant similar to that in Embodiment 1 is
used and circulated in the refrigerant circuit.
[0059] Subsequently, an operation of the air conditioner in a
heating operation according to this Embodiment will be described on
the basis of a flow of the refrigerant. Arrows along the
refrigerant circuit shown in FIG. 6 represent a flow of the
refrigerant in the heating operation. The high-temperature and
high-pressure gas refrigerant pressurized by compression of the
compressor 21 and discharged flows into the indoor unit 61 through
the piping. In the indoor unit 61, the refrigerant having passed
through the indoor heat exchanger 26 is condensed and liquefied. At
this time, the refrigerant radiates heat to the indoor air fed into
by the indoor heat exchanger fan 34, by which the indoor air as a
target of the heat exchange is heated. The heated indoor air is
supplied into a room as a hot air. The liquefied refrigerant is
decompressed while passing through the expanding means 23. Then,
the decompressed refrigerant is evaporated while passing through
the outdoor heat exchanger 25 and gasified. The gasified
refrigerant is sucked into the compressor 21 again.
[0060] Here, the expanding means 23 of the indoor unit 61 controls
a flow rate of the refrigerant passing through the indoor heat
exchanger 26. For example, if the temperature of the space to be
air-conditioned where the indoor unit 61 is installed reaches a
target temperature, the indoor unit 61 is brought into a thermo-off
state, the indoor heat exchanger fan 34 is stopped, and the
expanding means 23 is fully closed. Here, the closed state in this
Embodiment means the minimum opening degree to such a degree that
the refrigerant does not flow. Thus, the refrigerant does not pass
through the indoor heat exchanger 26 in the thermo-off state.
[0061] While the air conditioner is performing the heating
operation, the indoor heat exchanger 26 functions as a condenser,
but if either one of the indoor units 61a and 61b is brought into
the thermo-off state, the expanding means 23 of the indoor unit 61
is fully closed, and the refrigerant no longer passes through the
indoor heat exchanger 26. Thus, the number of condensers (heat
exchangers on the high pressure side) is rapidly decreased, and the
refrigerant pressure on the high pressure side is raised.
[0062] In the past, the indoor unit 61 is brought into the
thermo-off state, and feedback control is executed so that the
raised pressure of the refrigerant on the high pressure side gets
close to the target pressure. However, if the refrigerant having
double bond is circulated, overshoot of the refrigerant pressure
should be prevented in order to prevent decomposition of the
refrigerant.
[0063] Therefore, if the control means 53 determines that the
temperature of the space to be air-conditioned detected by
temperature detecting means (not shown) provided on the indoor unit
61, for example, reaches the target temperature, the control means
controls operations of the means constituting the refrigerating
cycle device such as stop of refrigerant inflow into the indoor
heat exchanger 26 by fully closing the expanding means 23, stop of
the indoor heat exchanger fan 34 and the like before stop of the
supply of a heat quantity to the indoor heat exchanger 26
(condenser) or substantially at the same time as the stop of the
supply of a heat quantity so that the refrigerant pressure on the
high pressure side of the refrigerant circuit is lowered. As a
result, the refrigerant pressure does not exceed the minimum
critical pressure, and the refrigerant is prevented from being
decomposed.
[0064] Here, with regard to the control to lower the refrigerant
pressure executed by the control means 53, control by means
(expanding means 23, indoor heat exchanger fan 34) on the side of
the indoor unit 61 continuing operations is practically difficult.
There can be measures such that the compressor frequency is lowered
by a predetermined number if the compressor 21 is a compressor
having an inverter circuit or control is made so that the fan
rotation number of the outdoor heat exchanger fan 33 is decreased.
Basically, control of operation of the compressor 21 has an
immediate effect and effective in lowering the pressure, but the
compressor 21 and the outdoor heat exchanger fan 33 may be
controlled in combination.
[0065] As mentioned above, as in Embodiment 2, in the refrigerating
cycle device such as an air conditioner in which the plurality of
indoor units 61 are connected in parallel and the indoor heat
exchanger 26 in the indoor unit 61 functions as a condenser as in
the heating operation, for example, in order to prevent rapid rise
of the refrigerant pressure on the high pressure side and exceeding
of the minimum critical pressure since the refrigerant suddenly
stops passing in the corresponding indoor heat exchanger 26 or the
indoor heat exchanger fan 34 is stopped and heat quantity of the
refrigerant cannot be emitted due to full closing of at least one
unit of the expanding means 23, before or substantially at the same
time when the expanding means 23 is fully closed, the control means
53 controls the operation of the compressor 21, for example, so as
to lower the refrigerant pressure on the outlet side of the
compressor 21 and to prevent the pressure from exceeding the
minimum critical pressure. Thus, the refrigerant containing a
chemically unstable substance having double bond can be prevented
from being attacked by decomposition of the substance itself having
double bond or decomposition of substances of the other
refrigerants in the mixed refrigerant and decomposed so as to stop
functioning as the refrigerant. Therefore, the performances of the
refrigerating cycle device can be maintained for a long time, and
moreover, reliability can be ensured.
Embodiment 3
[0066] FIG. 7 is a diagram illustrating a configuration of an air
conditioner according to Embodiment 3 of the present invention. In
this Embodiment, the air conditioner will be described. In FIG. 7,
means and the like given the same reference numerals as those in
FIG. 6 are means basically performing the same operations as the
operations described above. In FIG. 7, in the indoor units 61a and
61b, at positions opposing the indoor heat exchangers 26a and 26b
with respect to the expanding means 23a and 23b (the side where the
liquid refrigerant or the gas-liquid two-phase refrigerant flows,
the upstream side in the cooling operation), flow-passage
opening/closing means 29a and 29b are installed, respectively. The
flow-passage opening/closing means 29a and 29b are means for
adjusting (controlling) a flow rate of the refrigerant similarly to
the expanding means 23a and 23b. However, they are not capable of
fine flow-rate control as the expanding means 23a and 23b but if
they are opened, the refrigerant is made to pass, while if they are
closed, the refrigerant is not made to pass. Also, pressure
detecting means 42a and 42b are installed between the expanding
means 23a and 23b and the flow-passage opening/closing means 29a
and 29b. The control in this Embodiment is also executed by the
control means 53.
[0067] While the air conditioner is performing the cooling
operation, for example, the expanding means 23 of the indoor unit
61 is controlling a flow rate of the refrigerant to flow into the
indoor heat exchanger 26 and to be passed. If the temperature of
the space to be air-conditioned in which the indoor unit 61 is
installed gets close to the target temperature, for example,
control is made so that the expanding means 23 is throttled to a
direction where an opening area is gradually reduced, for example.
Then, when the temperature of the space to be air-conditioned
reaches the target temperature, the flow-passage opening/closing
means 29 is brought into a closed state so that the refrigerant
does not flow into the indoor heat exchanger 26.
[0068] Here, if the expanding means 23 is throttled till the
refrigerant flow rate reaches zero, the expanding means 23 is
considered to be fully closed. In this case, the liquid refrigerant
is sealed in the piping between the flow-passage opening/closing
means 29 and the expanding means 23. The sealed liquid refrigerant
is gasified if being heated from the periphery, and its volume is
rapidly increased. Gasification (evaporation) of the refrigerant
rapidly raises the refrigerant pressure. In this way, since the
pressure is raised in a portion where the refrigerant
(particularly, the liquid refrigerant) is sealed, the minimum
critical pressure might be exceeded, and the refrigerant is likely
to be decomposed.
[0069] Then, in the air conditioner of this Embodiment, pressure
detecting means 42 is installed between the flow-passage
opening/closing means 29 and the expanding means 23 in order to
prevent the refrigerant from being located in a sealed state by
enlarging the opening area of the expanding means 23 before the
refrigerant pressure relating to detection by the pressure
detecting means 42 exceeds the lowest critical pressure and to
prevent decomposition of the refrigerant caused by pressure
rise.
[0070] Also, if a space between the flow-passage opening/closing
means 29 and the expanding means 23 is sealed, too, heat is applied
here from the outside, and a problem will not occur unless the
liquid in this sealed section is evaporated and gasified. Since a
latent heat quantity for the refrigerant to be evaporated is large,
even if the space between the flow-passage opening/closing means 29
and the expanding means 23 is sealed, the refrigerant pressure is
not raised immediately. Thus, even without providing the pressure
detecting means 42 between the flow-passage opening/closing means
29 and the expanding means 23, by executing control of the control
means 53 such that the flow-passage'opening/closing means 29 or the
expanding means 23 is brought into an open state after a
predetermined time has elapsed since determination that the piping
between the expanding means 23 and the flow-passage opening/closing
means 29 is sealed, the pressure rise can be prevented, and the
similar effect can be obtained.
[0071] Also, not only the above-mentioned space between the
expanding means 23 and the flow-passage opening/closing means 29,
the same applies to a configuration having a structure that can
seal the refrigerant in the refrigerant circuit (if a plurality of
expanding means are connected in series by piping or the like). In
that case, too, the rise of the refrigerant pressure can be
prevented and the decomposition of the refrigerant can be prevented
not by sealing the refrigerant such that the expanding means 23 is
prevented from being fully closed, for example.
[0072] As mentioned above, according to Embodiment 3, by
controlling the refrigerant flow-rate by plural means such as the
space between the expanding means 23 and the flow-passage
opening/closing means 29, for example, if it is determined that the
refrigerant is sealed, the control means 53 executes control such
that at least one (the expanding means 23, here) is opened, the
rapid rise of the refrigerant pressure in the sealed state is
prevented, and exceeding of the lowest critical pressure can be
prevented. Thus, the refrigerant containing a chemically unstable
substance having double bond can be prevented from being attacked
by decomposition of the substance itself having double bond or
decomposition of the substances of the other refrigerants in the
mixed refrigerant and decomposed so as to stop functioning as the
refrigerant. Therefore, performances of the refrigerating cycle
device can be maintained for a long time, and moreover, reliability
can be ensured.
[0073] At this time, since the pressure detecting means 42 is
installed at a location which might be in a sealed state, the
control means 53 can make more detailed determination or the like
concerning the sealing of the refrigerant. Also, the control means
53 determines a state in the control of the expanding means 23 and
the flow-passage opening/closing means 29, for example, and if it
determines that the space between the expanding means 23 and the
flow-passage opening/closing means 29 is in a sealed state, the
control means makes control such that at least either one is opened
so as to release the sealed state after a predetermined period of
time, for example. And thus, the pressure detecting means 42 does
not have to be provided, which can contribute to cost
reduction.
Embodiment 4
[0074] In the above Embodiments, the mixed refrigerant was
described, but the present invention can be also applied to a
single refrigerant, which is a refrigerant made up of a substance
having double bond, for example. The lowest critical pressure in
this case is a critical pressure in the single refrigerant made up
of a substance having double bond. Not only to the substance having
double bond, can the present invention be also applied to a
situation including a refrigerant made up of a chemically unstable
substance.
INDUSTRIAL APPLICABILITY
[0075] In the above-mentioned Embodiments, the application to the
air conditioner capable of a cooling/heating operation was
described, but the present invention can also be applied to other
refrigerating cycle devices constituting a refrigerant circuit such
as a heat pump or the like.
REFERENCE SIGNS LIST
[0076] 21 compressor
[0077] 22 condenser
[0078] 23, 23a, 23b expanding means
[0079] 24 evaporator
[0080] 25 outdoor heat exchanger
[0081] 26a, 26b indoor heat exchanger
[0082] 27 four-way valve
[0083] 28 accumulator
[0084] 29a, 29b flow-passage opening/closing means
[0085] 31 condenser fan
[0086] 32 evaporator fan
[0087] 33 outdoor heat exchanger fan
[0088] 34a, 34b indoor heat exchanger fan
[0089] 41, 42a, 42b pressure detecting means
[0090] 51 pressure storage means
[0091] 52 critical pressure storage means
[0092] 53 control means
* * * * *