[0001] The present invention relates to a refrigerating cycle system using carbon dioxide
as the refrigerant.
[0002] FIG. 7 shows a known refrigerating cycle system using carbon dioxide (CO
2) as the refrigerant.
[0003] This refrigerating cycle system has a compressor 1, a radiator 2, an expansion valve
3, and a heat absorber 4; and circulates a CO
2 refrigerant sequentially in the order of the compressor 1 → the radiator 2 → the
expansion valve 3 → the heat absorber 4 → the compressor 1 as shown by arrows in FIG.
7. As a result, the heat of the air in a room is absorbed by the heat absorber 4,
and the room is cooled.
[0004] The room-cooling operation of this refrigerating cycle system will be described referring
to the Mollier diagram of FIG. 8. The compressor 1 compresses the CO
2 refrigerant (refrigerant pressure: 40 kg/cm
2) to a pressure exceeding the critical point of the saturated liquid line and the
saturated vapor line, for example, 100 kg/cm
2 (A → B of FIG. 8). Next, the compressed CO
2 refrigerant is discharged outdoors with the radiator 2 (B → C of FIG. 8). Then, the
heat-released CO
2 refrigerant is expanded along the isenthalpic line with the expansion valve 3 to
lower the pressure (C → D of FIG. 8). The CO
2 refrigerant that becomes the wet vapor due to this pressure lowering absorbs heat
from the air in the room in the heat absorber. Thereby, the room is cooled (D → A
of FIG. 8).
[0005] Thus, in order to obtain a desired refrigerating capacity even in summer when the
outdoor temperature is high, the refrigerating cycle system that discharges heat outdoors
requires a compressor that obtains a high discharging pressure.
[0006] However, even though this refrigerating cycle system employs a compressor 1 of a
large refrigerating capacity, the operation efficiency is lower than the operation
efficiency of refrigerating cycle systems using chlorofluorocarbon-based and hydrocarbon-based
refrigerants.
[0007] In consideration of such problems, the present applicant proposed a refrigerating
cycle system as described in Japanese Patent Laid-open No. 11-94379. In this refrigerating
cycle system, a compressor 1 is composed of a first compressor (not shown) and a second
compressor (not shown); a radiator 2 is composed of a first radiator (not shown) and
a second radiator (not shown); and the rotating drive shaft of the second compressor
and the rotating output shaft of the expansion mechanism are connected to each other.
A CO
2 refrigerant is sequentially circulated in the order of the first compressor → the
first radiator → the second compressor → the second radiator → the expansion mechanism
→ the heat absorber → the first compressor.
[0008] According to this refrigerating cycle system, the refrigerant is compressed by the
first compressor, the compressed refrigerant is discharged by the first radiator,
the discharged the refrigerant is compressed by the second compressor, and the compressed
refrigerant is discharged by the second radiator. The use of the first compressor
and the second compressor reduces the power for the entire compressor.
[0009] The object of the present invention is to provide a refrigerating cycle system that
has a different structure from the refrigerating cycle system disclosed in Japanese
Patent Laid-Open No. 11-94379, that can obtain a desired refrigerating pressure without
increasing the power for the entire compressor, and that has an improved refrigerating
effect.
[0010] The present invention is a refrigerating cycle system having a refrigerant pipe for
circulating a carbon dioxide refrigerant sequentially to a first compressor, a first
radiator, an expansion mechanism, and a heat absorber, and discharging heat from the
first radiator in a supercritical state, wherein a second compressor is provided in
the refrigerant pipe between the heat absorber and the first compressor, and the rotating
drive shaft of the second compressor and the rotating output shaft of the expansion
mechanism are connected to each other.
[0011] According to the present invention, a CO
2 refrigerant is sequentially circulated in the order of the second compressor → the
first compressor → the radiator → the expansion mechanism → the heat absorber → the
second compressor to cool rooms and the like. In this refrigerating cycle, since the
drive force of the second compressor is obtained from the power generated by the refrigerant
expansion action of the expansion mechanism, a small power suffices to drive the first
compressor, and energy from external sources can be minimized.
[0012] The above-described object and other objects, features, and advantages of the present
invention will be obviously understood from the following description and attached
drawings.
[0013] In the Drawings:
FIG. 1 is a refrigerant circuit diagram of a refrigerating cycle system according
to the first embodiment;
FIG. 2 is a schematic diagram showing the connecting structure of a second compressor
with an expansion mechanism according to the first embodiment;
FIG. 3 is a Mollier diagram of a refrigerating cycle system according to the first
embodiment;
FIG. 4 is a refrigerant circuit diagram of a refrigerating cycle system according
to the second embodiment;
FIG. 5 is a refrigerant circuit diagram of a refrigerating cycle system according
to the third embodiment;
FIG. 6 is a Mollier diagram of a refrigerating cycle system according to the third
embodiment;
FIG. 7 is a refrigerant circuit diagram of a conventional refrigerating cycle system;
and
FIG. 8 is a Mollier diagram of a conventional refrigerating cycle system.
[0014] FIGS. 1 to 3 show the first embodiment of refrigerating cycle systems according to
the present invention. The same components as previously in the above described conventional
examples referring to FIG. 7 and FIG. 8 are denoted by the same numerals and characters.
[0015] This refrigerating cycle system uses CO
2 as the refrigerant. As FIG. 1 shows, the refrigerating cycle system sequentially
connects a first compressor 1a, a first radiator 2a, an expansion mechanism 3a, a
heat absorber 4, and a second compressor 1b using a refrigerant pipe 5. The refrigerating
cycle system circulates the CO
2 refrigerant sequentially in the order of the second compressor 1b → the first compressor
1a → the first radiator 2a → the expansion mechanism 3a → the heat absorber 4 → the
second compressor 1b as shown by solid-line arrows in FIG. 1, to cool rooms utilizing
the heat-absorbing action of the heat absorber 4.
[0016] In the refrigerating cycle system thus constituted, both the second compressor 1b
and the expansion mechanism 3a have the constitution as shown in FIG. 2, that is,
adopt a scroll-type compression/expansion mechanism.
[0017] The second compressor 1b has a gas inlet 11 at the outer portion and a gas outlet
12 at the center portion, and a rotating scroll 13 is rotated in the arrow direction
in FIG. 2 (clockwise to FIG. 2). Thereby the CO
2 refrigerant is sucked from the gas inlet 11, which is compressed between the rotating
scroll 13 and the stationary scroll 14, and the compressed CO
2 refrigerant is discharged from the gas outlet 12.
[0018] The expansion mechanism 3a has the inverted constitution to the second compressor
1b. Specifically, the expansion mechanism 3a has a gas outlet 31 at the outer portion
and a gas inlet 32 at the inner portion, and a rotating scroll 33 is rotated in the
arrow direction in FIG. 2 (counterclockwise to FIG. 2). Thereby the CO
2 refrigerant is sucked from the gas inlet 32, expanded between the rotating scroll
33 and the stationary scroll 34, and discharged from the gas outlet 31.
[0019] The rotating drive shaft of the second compressor 1b is connected to the rotating
output shaft of the expansion mechanism 3a with a shaft 6 as FIG. 2 shows, and the
driving of the expansion mechanism 3a drives the second compressor 1b.
[0020] Next, the change in the refrigerant of the refrigerating cycle system according to
the present invention will be described. First, when the first compressor 1a is operated,
the CO
2 refrigerant is compressed, and the pressure thereof is applied through the first
radiator 2a to the gas inlet 32 of the expansion mechanism 3a. Thereby, the expansion
mechanism 3a is rotated, and the rotation force of the expansion mechanism 3a rotates
the second compressor 1b.
[0021] By such operations of the first compressor 1a, the second compressor 1b, and the
expansion mechanism 3a, the CO
2 refrigerant is compressed by the second compressor 1b, and further compressed by
the first compressor 1a. The refrigerant after two-stage compression is radiated by
the first radiator 2a installed outdoors. The pressure of the radiated CO
2 refrigerant is reduced in the expansion mechanism 3a, and the refrigerant absorbs
heat in the heat absorber 4 from the air in the room, and is sucked into the second
compressor 1b.
[0022] The above-described refrigerating cycle system will be described referring to the
Mollier diagram shown in FIG. 3. The CO
2 refrigerant is compressed in the second compressor 1b, for example, from 40 kg/cm
2 to P1 kg/cm
2 (A → B1). In the first compressor 1a, the refrigerant is further compressed from
P1 kg/cm
2 to about 100 kg/cm
2 (B1 → B). Next, it is radiated in the first radiator 2a (B → C), and thereafter,
the pressure of the refrigerant is reduced from 100 kg/cm
2 to 40 kg/cm
2 along the isentropic line (C → D1). Then the pressure-reduced CO
2 refrigerant is circulated again into the second compressor 1b (D1 → A).
[0023] Here, A → B → C → D shown in FIG. 3 is of a conventional example (an example wherein
the refrigerant pressure is changed 40 kg/cm
2 to 100 kg/cm
2 by the first compressor 1a alone), and (h) denotes enthalpy. The cooling action of
the refrigerating cycle system according to the present invention will be described
comparing to the cooling action of the refrigerating cycle system according to a conventional
example.
[0024] The power (WA1) of a compressor in the conventional refrigerating cycle system is:
[0025] On the other hand, the refrigerating cycle system according to the present invention
has a structure wherein the rotating drive shaft of the first compressor 1b is connected
to the rotating output shaft of the expansion mechanism 3a with a common shaft 6.
As a result, the power generated by the refrigerant-expanding action of the expansion
mechanism 3a is utilized for the refrigerant-compressing action of the second compressor
1b. Therefore, the power (WA2) of the compressor 1a is as follows:
Also, the refrigerating effect (WB1) of the conventional refrigerating cycle system
is as follows:
On the other hand, the refrigerating effect (WB2) of the refrigerating cycle system
according to the present invention is as follows:
Furthermore, the cop (coefficient of performance) (εγ1) of the conventional refrigerating
cycle system is as follows:
The COP (εγ2) of the refrigerating cycle system according to the present invention
is as follows:
Here, as FIG. 3 shows, since WA1 > WA2, and WB1 < WS2, each COP is as follows:
[0026] Therefore, the refrigerating cycle system according to the present invention consumes
less power than the conventional refrigerating cycle system, and also excels in COP.
Since the expansion mechanism 3a of the refrigerating cycle system according to the
present invention adiabatically expands the CO
2 refrigerant, the refrigerant pressure changes along the isentropic line, and the
refrigerating effect is improved.
[0027] FIG. 4 shows the second embodiment of the refrigerating cycle system. In the drawing,
the same components as in the above-described first embodiment are denoted by the
same reference numerals and characters, the description thereof will be omitted.
[0028] In the second embodiment, a bypass pipe 7 that bypasses the second compressor 1b
is installed in the refrigerant pipe 5 wherein the above-described second compressor
1b is installed. One end of the bypass pipe 7 is connected to the refrigerant pipe
5 connected to the gas inlet 31 of the second compressor 1b, and the other end of
the bypass pipe 7 is connected to the refrigerant pipe 5 connected to the gas outlet
32 of the second compressor 1b. A switching valve 8 is installed in the middle of
the bypass pipe 7.
[0029] According to this embodiment, the switching valve 8 is opened when the operation
of the first compressor 1a is started. Thereby, as the solid-line arrows in FIG. 4
show, the CO
2 refrigerant is sucked into the suction side of the first compressor 1a through the
bypass pipe 7, and the pressure in the suction side of the expansion mechanism 3a
is elevated. concurrent with the pressure elevation, the expansion mechanism 3a is
driven, and the second compressor 1b is also driven. Then, after the expansion mechanism
3a and the second compressor 1b have been driven, the switching valve 8 is closed.
Thereby, as dashed-line arrows in FIG. 4 show, the entire CO
2 refrigerant is circulated into the second compressor 1b, and the operation shifts
to the steady operation.
[0030] According to this embodiment, when the operation of the first compressor 1a is started,
the suction pressure of the expanding mechanism 3a is rapidly elevated, and shift
to the steady operation is smoothly accomplished in a short time.
[0031] FIGS. 5 and 6 show the third embodiment of the refrigerating cycle system. In the
drawings, the same components as in the above-described second embodiment are denoted
by the same reference numerals and characters, the description thereof will be omitted.
[0032] In the third embodiment, the refrigerant pipe 5 between the first compressor 1a and
the second compressor 1b is provided with a second radiator 2b. According to this
embodiment, the switching valve 8 is opened when the operation of the first compressor
1a. Thereby, as the solid-line arrows in FIG. 5 show, a CO
2 refrigerant is sucked into the suction side of the first compressor 1a through a
bypass pipe 7 and a second radiator 2b, and the pressure in the suction side of the
expanding mechanism 3a is elevated, concurrent with the pressure elevation, the expansion
mechanism 3a is driven, and the second compressor 1b is also driven. Then, after the
expansion mechanism 3a and the second compressor 1b have been driven, the switching
valve 8 is closed. Thereby, as dashed-line arrows in FIG. 5 show, the entire CO
2 refrigerant is circulated into the second compressor 1b, and the operation shifts
to the steady operation.
[0033] The cooling cycle in such a steady operation will be described referring to the Mollier
diagram of FIG. 6. The CO
2 refrigerant is compressed in the second compressor 1b, for example, from 40 kg/cm
2 to P2 kg/cm
2 (A → B1). The compressed CO
2 refrigerant is radiated in the second radiator 2b (B1 → C1). In the first compressor
1a, the radiated CO
2 refrigerant is further compressed from P2 kg/cm
2 to 100 kg/cm
2 (C1 → B2). Next, it is radiated in the first radiator 2a (B2 → C), and thereafter,
in the expanding mechanism 3a the pressure of the refrigerant is reduced from 100
kg/cm
2 to 40 kg/cm
2 along the isentropic line (C → D1). Then the pressure-reduced CO
2 refrigerant is circulated again into the second compressor 1b (D1 → A).
[0034] Here, A → B → C → D1 shown in FIG. 6 shows the refrigerant change of the refrigerating
cycle system according to the above-described first embodiment. The cooling action
of the refrigerating cycle system according to this embodiment will be described below
comparing with the cooling action of the refrigerating cycle system according to the
above-described first embodiment.
[0035] The power (WA2) of the compressor 1a of the refrigerating cycle system according
to the above-described first embodiment is as follows:
The power (WA3) of the compressor 1a of the refrigerating cycle system according
to this embodiment is as follows:
Here, each power WA2 and WA3 is as follows as FIG. 6 shows:
This is because the refrigerant sucked into the first compressor 1a is partly radiated
in the second radiator 2b, and the power is reduced by decrease in enthalpy (by increase
in the gradient of isentropic line in the first compressor 1a greater than the gradient
of isentropic line in the second compressor 1b).
[0036] Therefore, in the refrigerating cycle system according to this embodiment, the power
of the compressor 1a further decreases, and the refrigerating cycle system excels
in energy saving.