U.S. patent application number 13/140331 was filed with the patent office on 2011-10-13 for refrigeration cycle apparatus.
This patent application is currently assigned to PANASONIC CORPORATION. Invention is credited to Takumi Hikichi, Masaya Honma, Takeshi Ogata, Yu Shiotani, Masanobu Wada.
Application Number | 20110247358 13/140331 |
Document ID | / |
Family ID | 42287235 |
Filed Date | 2011-10-13 |
United States Patent
Application |
20110247358 |
Kind Code |
A1 |
Wada; Masanobu ; et
al. |
October 13, 2011 |
REFRIGERATION CYCLE APPARATUS
Abstract
A refrigeration cycle apparatus 100 is provided with a working
fluid circuit 106 and a first bypass passage 112. The working fluid
circuit 106 is formed of a first compressor 101, a heat radiator
102, an expander 103, an evaporator 104, a second compressor 105,
and flow passages 106a to 106e connecting these components in this
order. The expander 103 and the second compressor 105 are coupled
to each other by a power-recovery shaft 107 so that the second
compressor 105 is driven by the power recovered by the expander
103. The first bypass passage 112 communicates between a portion
from the discharge port of the first compressor 101 to the suction
port of the expander 103 in the working fluid circuit 106 and a
portion from the outlet of the evaporator 104 to the suction port
of the second compressor 105 in the working fluid circuit 106, at
the time of activation of the refrigeration cycle apparatus
100.
Inventors: |
Wada; Masanobu; (Osaka,
JP) ; Hikichi; Takumi; (Shiga, JP) ; Shiotani;
Yu; (Osaka, JP) ; Ogata; Takeshi; (Osaka,
JP) ; Honma; Masaya; (Osaka, JP) |
Assignee: |
PANASONIC CORPORATION
Kadoma-shi, Osaka
JP
|
Family ID: |
42287235 |
Appl. No.: |
13/140331 |
Filed: |
December 21, 2009 |
PCT Filed: |
December 21, 2009 |
PCT NO: |
PCT/JP2009/007066 |
371 Date: |
June 16, 2011 |
Current U.S.
Class: |
62/510 |
Current CPC
Class: |
F25B 2400/14 20130101;
F25B 1/10 20130101; F25B 2600/01 20130101; F25B 2309/061 20130101;
F25B 9/06 20130101; F25B 9/008 20130101; F25B 2500/26 20130101;
F25B 2700/191 20130101; F25B 2400/0401 20130101 |
Class at
Publication: |
62/510 |
International
Class: |
F25B 1/10 20060101
F25B001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2008 |
JP |
2008-325208 |
Claims
1. A refrigeration cycle apparatus comprising: a working fluid
circuit formed of a first compressor for compressing a working
fluid, a heat radiator for cooling the working fluid compressed by
the first compressor, an expander for expanding the working fluid
cooled by the heat radiator and recovering power from the working
fluid, an evaporator for evaporating the working fluid expanded by
the expander, a second compressor for increasing the pressure of
the working fluid evaporated by the evaporator and supplying it to
the first compressor, and flow passages connecting these components
in this order; a power-recovery shaft coupling the expander to the
second compressor so that the second compressor is driven by the
power recovered by the expander; a first bypass passage for
communicating between a portion from a discharge port of the first
compressor to a suction port of the expander in the working fluid
circuit and a portion from an outlet of the evaporator to a suction
port of the second compressor in the working fluid circuit; and a
first bypass valve for controlling flow of the working fluid in the
first bypass passage, the first bypass valve being provided on the
first bypass passage.
2. The refrigeration cycle apparatus according to claim 1, further
comprising: an activation assist valve provided on the working
fluid circuit at a point that is located between the outlet of the
evaporator and the suction port of the second compressor and that
is closer to the evaporator than a downstream end of the first
bypass passage is.
3. The refrigeration cycle apparatus according to claim 2, wherein
the first bypass valve is provided in an upstream end section or a
downstream end section of the first bypass passage.
4. The refrigeration cycle apparatus according to claim 2, wherein
the first bypass valve is an on-off valve or a three-way valve.
5. The refrigeration cycle apparatus according to claim 1, further
comprising: a second bypass passage for communicating between a
portion from a discharge port of the expander to a downstream end
of the first bypass passage in the working fluid circuit and a
portion from a discharge port of the second compressor to a suction
port of the first compressor in the working fluid circuit.
6. The refrigeration cycle apparatus according to claim 5, further
comprising: a second bypass valve for controlling flow of the
working fluid in the second bypass passage, the second bypass valve
being provided on the second bypass passage.
7. The refrigeration cycle apparatus according to claim 2, wherein
the first bypass valve is opened before activation of the first
compressor or in response to the activation of the first
compressor.
8. The refrigeration cycle apparatus according to claim 2, wherein
the first bypass valve is closed after activation of the second
compressor.
9. The refrigeration cycle apparatus according to claim 8, further
comprising: an activation detector for detecting the activation of
the second compressor; and a controller for controlling opening and
closing of the first bypass valve, wherein the controller detects
the activation of the second compressor by receiving a detection
signal from the activation detector, and closes the first bypass
valve.
10. The refrigeration cycle apparatus according to claim 9, wherein
the activation detector is a temperature detector for detecting a
difference between a temperature of the working fluid to be drawn
into the expander and a temperature of the working fluid discharged
from the expander, and the activation of the second compressor is
detected when the temperature difference exceeds a specific
value.
11. The refrigeration cycle apparatus according to claim 9, wherein
the activation detector is a pressure detector for detecting a
difference between a pressure of the working fluid to be drawn into
the expander and a pressure of the working fluid discharged from
the expander, and the activation of the second compressor is
detected when the pressure difference exceeds a specific value.
12. The refrigeration cycle apparatus according to claim 9, wherein
the activation detector is a timer for measuring time elapsed from
a time point of activation of the first compressor, and the
activation of the second compressor is detected when the time
measured by the timer exceeds a specific time.
13. The refrigeration cycle apparatus according to claim 2, wherein
the activation assist valve is closed before activation of the
first compressor, or in response to the activation of the first
compressor.
14. The refrigeration cycle apparatus according to claim 2, wherein
the activation assist valve is opened after activation of the
second compressor.
15. The refrigeration cycle apparatus according to claim 14,
further comprising: an activation detector for detecting the
activation of the second compressor; and a controller for
controlling opening and closing of the activation assist valve,
wherein the controller detects the activation of the second
compressor by receiving a detection signal from the activation
detector, and opens the activation assist valve.
16. The refrigeration cycle apparatus according to claim 15,
wherein the activation detector is a temperature detector for
detecting a difference between a temperature of the working fluid
to be drawn into the expander and a temperature of the working
fluid discharged from the expander, and the activation of the
second compressor is detected when the temperature difference
exceeds a specific value.
17. The refrigeration cycle apparatus according to claim 15,
wherein the activation detector is a pressure detector for
detecting a difference between a pressure of the working fluid to
be drawn into the expander and a pressure of the working fluid
discharged from the expander, and the activation of the second
compressor is detected when the pressure difference exceeds a
specific value.
18. The refrigeration cycle apparatus according to claim 15,
wherein the activation detector is a timer for measuring time
elapsed from a time point of activation of the first compressor,
and the activation of the second compressor is detected when the
time measured by the timer exceeds a specific time.
19. The refrigeration cycle apparatus according to claim 1, wherein
the expander and the second compressor are accommodated in a single
closed casing.
20. The refrigeration cycle apparatus according to claim 1, wherein
the first bypass valve is a three-way valve provided at a junction
of the downstream end of the first bypass passage and the portion
from the outlet of the evaporator to the suction port of the second
compressor in the working fluid circuit.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigeration cycle
apparatus.
BACKGROUND ART
[0002] A refrigeration cycle apparatus 500 shown in FIG. 9 is
conventionally known as a refrigeration cycle apparatus provided
with an expander that recovers power by expanding a working fluid,
and a second compressor that preliminarily increases the pressure
of the working fluid (for example, see JP 2003-307358 A). With
reference to FIG. 9, the configuration of the conventional
refrigeration cycle apparatus 500 is described.
[0003] As shown in FIG. 9, the refrigeration cycle apparatus 500 is
provided with a working fluid circuit 6 formed of a first
compressor 1, a heat radiator 2, an expander 3, an evaporator 4, a
second compressor 5, and flow passages 10a to 10e connecting these
components in this order. The second compressor 5 is coupled to the
expander 3 by a power-recovery shaft 7, and is driven by receiving
mechanical energy recovered by the expander 3, via the
power-recovery shaft 7.
[0004] Further, a bypass passage 8 that bypasses the second
compressor 5, and a bypass valve 9 that controls the flow of the
working fluid in the bypass passage 8 are provided therein. The
upstream end of the bypass passage 8 is connected to the flow
passage 10d connecting the outlet of the evaporator 4 and the
suction port of the second compressor 5. The downstream end of the
bypass passage 8 is connected to the flow passage 10e connecting
the discharge port of the second compressor 5 and the suction port
of the first compressor 1.
[0005] The refrigeration cycle apparatus 500 is activated according
to the following procedures. First, the first compressor 1 starts
operating, and the bypass valve 9 is opened. This allows the
working fluid in the evaporator 4 to be drawn into the first
compressor 1 through the bypass passage 8 as shown by solid arrows
in FIG. 9. The working fluid with the pressure increased in the
first compressor 1 is discharged therefrom, thereby causing an
increase in the pressure at the suction port of the expander 3. As
a result of this, a pressure difference is caused between before
and after the expander 3, as shown in FIG. 10, so that the expander
3 and the second compressor 5 can be activated rapidly. After the
expander 3 and the second compressor 5 are activated, the bypass
valve 9 is closed. The working fluid flowing out of the evaporator
4 is drawn into the second compressor 5 through the flow passage
10d, as shown by dashed arrows in FIG. 9. In this way, a smooth
transfer to regular operation can be achieved by providing the
bypass passage 8.
CITATION LIST
Patent Literature
[0006] Patent Literature 1: JP 2003-307358 A
SUMMARY OF INVENTION
Technical Problem
[0007] In the refrigeration cycle apparatus 500, only the expander
3 is involved in the activation of the expander 3 and the second
compressor 5, whereas the second compressor 5 does not contribute
thereto. Rather, the second compressor 5 acts as a load at the time
of activation of the expander 3. That is, friction or the like
between the power-recovery shaft 7 and the component parts of the
second compressor 5 acts as a driving resistance in the expander
3.
[0008] Meanwhile, in the regular operation of the refrigeration
cycle apparatus 500, the second compressor 5 and the expander 3 are
coupled to each other by the power-recovery shaft 7 that is
commonly shared therebetween and thus have identical rotation
rates, as well as forming the working fluid circuit 6 of a single
channel. Accordingly, the volume of the second compressor 5 and the
volume of the expander 3 need to be set so that the mass of the
working fluid to be drawn by the second compressor 5 per unit time
is equal to the mass of the working fluid to be drawn by the
expander 3 per unit time.
[0009] FIG. 11 is a Mollier diagram when carbon dioxide is used as
the working fluid in the conventional refrigeration cycle apparatus
500. As shown in FIG. 11, in the regular operation of the
conventional refrigeration cycle apparatus 500, the working fluid
drawn by the second compressor 5 has a pressure of 40 kg/cm.sup.2
and a temperature of about 10.degree. C. (point A in FIG. 11). At
this time, the working fluid has a density of 108.0 kg/m.sup.3. The
working fluid drawn by the expander 3 has a pressure of 100
kg/cm.sup.2 and a temperature of 40.degree. C. (point C in FIG.
11). At this time, the working fluid has a density of 628.61
kg/m.sup.3.
[0010] Here, the suction volume (m.sup.3) of the second compressor
5 is referred to as Vc, the suction volume (m.sup.3) of the
expander 3 is referred to as Ve, and the rotation rate (S.sup.-1)
of the power-recovery shaft 7 per second is referred to as N. The
mass (kg/s) of the working fluid that the second compressor 5 can
draw per second and the mass (kg/s) of the working fluid that the
expander 3 can draw per second can be expressed respectively by
Formula 1 and Formula 2.
(The mass of the working fluid that the second compressor 5 can
draw per second)=108.0.times.Vc.times.N Formula 1:
(The mass of the working fluid that the expander 3 can draw per
second)=628.61.times.Ve.times.N Formula 2:
[0011] When the mass of the working fluid that the second
compressor 5 can draw per second is equal to the mass of the
working fluid that the expander 3 can draw per second, the suction
volume Vc of the second compressor 5 can be expressed by
[0012] Formula 3 from the above-mentioned Formula 1 and Formula
2.
Vc=(628.61/108.0).times.Ve.apprxeq.5.8.times.Ve Formula 3:
[0013] That is, the expander 3 needs to drive the second compressor
5 having a suction volume that is about 5.8 times that of the
expander 3, at the time of activation of the refrigeration cycle
apparatus 500. Further, the larger the ratio between the density of
the working fluid to be drawn by the second compressor 5 and the
density of the working fluid to be drawn by the expander 3, the
larger the ratio between the suction volume of the second
compressor 5 and the suction volume of the expander 3 also should
be. In other words, the suction volume of the expander 3 becomes
smaller with respect to the suction volume of the second compressor
5, and the driving resistance of the expander 3 at the time of
activation of the second compressor 5 relatively increases.
Accordingly, there is a possibility that the expander 3 cannot
drive the second compressor 5 at the time of activation, depending
on the operational conditions of the refrigeration cycle apparatus
500. Instead, it might be necessary to impose an excess pressure,
as compared to that in the regular operation, on the suction port
side of the expander 3, so that a driving force necessary to drive
the second compressor 5 should be obtained, possibly resulting in a
problem of safety, such as pressure resistance.
[0014] The present invention aims to solve the above-mentioned
conventional problems, and it is an object of the present invention
to provide a refrigeration cycle apparatus that can be activated
surely and stably.
Solution to Problem
[0015] That is, the present invention provide a refrigeration cycle
apparatus including: a working fluid circuit formed of a first
compressor for compressing a working fluid, a heat radiator for
cooling the working fluid compressed by the first compressor, an
expander for expanding the working fluid cooled by the heat
radiator and recovering power from the working fluid, an evaporator
for evaporating the working fluid that has been expanded by the
expander, a second compressor for increasing the pressure of the
working fluid that has been evaporated by the evaporator and
supplying it to the first compressor, and flow passages connecting
these components in this order; a power-recovery shaft coupling the
expander to the second compressor so that the second compressor is
driven by the power that has been recovered by the expander; a
first bypass passage for communicating between a portion from the
discharge port of the first compressor to the suction port of the
expander in the working fluid circuit and a portion from the outlet
of the evaporator to the suction port of the second compressor in
the working fluid circuit; and a first bypass valve, provided on
the first bypass passage, for controlling the flow of the working
fluid in the first bypass passage.
Advantageous Effects of Invention
[0016] According to the refrigeration cycle apparatus of the
present invention, a working fluid at high pressure that is
equivalent to one supplied to the suction port of the expander can
be supplied to the suction port of the second compressor at the
time of activation. On the other hand, the pressure at the
discharge port of the second compressor is equalized with that at
the suction port of the first compressor, that is, the pressure
becomes relatively low. In other words, a large pressure difference
can be caused between before and after the second compressor.
Therefore, the refrigeration cycle apparatus of the present
invention can be activated surely and stably independent of
operational conditions.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a configuration diagram of the refrigeration cycle
apparatus in Embodiment 1 of the present invention.
[0018] FIG. 2 is a flow chart of the activation control of the
refrigeration cycle apparatus in Embodiment 1 of the present
invention.
[0019] FIG. 3 is a configuration diagram of the refrigeration cycle
apparatus in Embodiment 2 of the present invention.
[0020] FIG. 4 is a flow chart of the activation control of the
refrigeration cycle apparatus in Embodiment 2 of the present
invention.
[0021] FIG. 5 is a configuration diagram of the refrigeration cycle
apparatus in Embodiment 3 of the present invention.
[0022] FIG. 6A is a schematic view showing the state at the time of
activation of the refrigeration cycle apparatus in Embodiments 1
and 2.
[0023] FIG. 6B is a schematic view showing the state at the time of
activation of the refrigeration cycle apparatus in Embodiment
3.
[0024] FIG. 7 is a configuration diagram of the refrigeration cycle
apparatus in Reference Example.
[0025] FIG. 8A is a schematic view showing the flow of the working
fluid at the time of activation of a conventional refrigeration
cycle apparatus.
[0026] FIG. 8B is a schematic view showing the flow of the working
fluid at the time of activation of the refrigeration cycle
apparatus in Embodiment 1, Embodiment 2 and Reference Example.
[0027] FIG. 9 is a configuration diagram of the conventional
refrigeration cycle apparatus.
[0028] FIG. 10 is a schematic view showing the state at the time of
activation of the refrigeration cycle apparatus shown in FIG.
9.
[0029] FIG. 11 is a Mollier diagram when carbon dioxide is used as
a working fluid in the conventional refrigeration cycle
apparatus.
DESCRIPTION OF EMBODIMENTS
[0030] Hereinafter, several embodiments of the present invention
are described with reference to the drawings. It should be noted
that the present invention is not limited to the following
embodiments.
Embodiment 1
<Configuration of Refrigeration Cycle Apparatus 100>
[0031] FIG. 1 is a configuration diagram showing a refrigeration
cycle apparatus 100 in Embodiment 1 of the present invention. As
shown in FIG. 1, the refrigeration cycle apparatus 100 is provided
with a working fluid circuit 106 formed by sequentially connecting
a first compressor 101, a heat radiator 102, an expander 103, an
evaporator 104 and a second compressor 105, with flow passages
(pipes) 106a to 106e. As a working fluid, a refrigerant such as
carbon dioxide can be used.
[0032] The first compressor 101 is constituted by arranging a
compression mechanism 101a and a motor 101b for driving the
compression mechanism 101a in a single closed casing 101c holding
lubrication oil. The first compressor 101 compresses the working
fluid to high temperature and high pressure. A scroll compressor or
a rotary compressor, for example, can be used as the first
compressor 101. The discharge port of the first compressor 101 is
connected to the inlet of the heat radiator 102 via the flow
passage 106a.
[0033] The heat radiator 102 allows the working fluid that has been
compressed to high temperature and high pressure by the first
compressor 101 to radiate heat. (The heat radiator 102 cools the
working fluid that has been compressed to high temperature and high
pressure by the first compressor 101.) The outlet of the heat
radiator 102 is connected to the suction port of the expander 103
via the flow passage 106b.
[0034] The expander 103 expands the working fluid that has flowed
out of the heat radiator 102 and is at intermediate temperature and
high pressure. The expander 103 converts the expansion energy
(power) of the working fluid into mechanical energy so as to
recover it. The discharge port of the expander 103 is connected to
the inlet of the evaporator 104 via the flow passage 106c. A scroll
expander or a rotary expander, for example, can be used as the
expander 103. In addition, a fluid pressure motor expander can be
used as the expander 103. The fluid pressure motor expander is a
fluid machine that recovers power from a working fluid by
sequentially performing processes of drawing the working fluid from
the heat radiator 102 and discharging the drawn working fluid into
the evaporator 104 without performing any substantial expansion
process in the working chamber. The detailed structure and the
operational principle of the fluid pressure motor expander is
disclosed, for example, in WO 2008/050654 A.
[0035] The evaporator 104 evaporates the working fluid at low
temperature and low pressure that has been expanded by the expander
103, by heating. The outlet of the evaporator 104 is connected to
the suction port of the second compressor 105 via the flow passage
106d.
[0036] The second compressor 105 draws the working fluid that has
flowed out of the evaporator 104 and is at intermediate temperature
and low pressure. The second compressor 105 discharges it into the
first compressor 101 after preliminarily increasing the pressure
thereof. The discharge port of the second compressor 105 is
connected to the suction port of the first compressor 101 via the
flow passage 106e. A scroll compressor or a rotary compressor can
be used as the second compressor 105. In addition, a fluid pressure
motor compressor can be used as the second compressor 105. The
fluid pressure motor compressor is a fluid machine that increases
the pressure of a working fluid by substantially sequentially
performing processes of drawing the working fluid from the
evaporator 104 and discharging the drawn working fluid into the
first compressor 101. In other words, the fluid pressure motor
compressor is a fluid machine that allows substantially no volume
change of the working fluid in a working chamber. The fluid
pressure motor compressor has basically the same structure as the
fluid pressure motor expander, and the above-mentioned literature
discloses it in detail.
[0037] The expander 103 and the second compressor 105 are
accommodated in a single closed casing 109 holding lubrication oil.
The expander 103 is coupled to the second compressor 105 by a
power-recovery shaft 107. The expander 103, the second compressor
105 and the power-recovery shaft 107 function as a power recovery
system 108 that drives the second compressor 105 by transferring
the mechanical energy (power) recovered by the expander 103 to the
second compressor 105 via the power-recovery shaft 107.
[0038] In Embodiment 1, the second compressor 105 has a larger
volume than the expander 103. The ratio (Vc/Ve) of the volume Vc of
the second compressor 105 with respect to the volume Ve of the
expander 103 is set, for example, to the range of 5 to 15.
Particularly, in the case of using a working fluid, such as carbon
dioxide, that forms a refrigeration cycle with a large pressure
difference, the ratio (Vc/Ve) also tends to be large. Generally,
the larger the ratio (Vc/Ve), the larger the driving force (torque)
is required for the self-activation of the power recovery system
108. In this regard, "the volume of the second compressor 105"
means a confined volume, that is, the volume of the working chamber
at the completion of the drawing process. This should be applied to
the volume of the expander 103 as well.
[0039] The refrigeration cycle apparatus 100 is further provided
with a first bypass passage 112 and a first bypass valve 113. The
first bypass passage 112 is connected to the working fluid circuit
106 so as to communicate between the flow passage 106b connecting
the outlet of the heat radiator 102 to the suction port of the
expander 103, and the flow passage 106d connecting the outlet of
the evaporator 104 to the suction port of the second compressor
105. The first bypass valve 113 is provided on the first bypass
passage 112, and controls the flow of the working fluid in the
first bypass passage 112.
[0040] The upstream end K1 of the first bypass passage 112 is
connected to the flow passage 106b, and the downstream end K2 of
the first bypass passage 112 is connected to the flow passage 106d.
That is, the first bypass passage 112 is a flow passage that allows
the working fluid in the flow passage 106b to be drawn directly
into the second compressor 105, before the power-recovery shaft 107
is rotated, while bypassing the expander 103 and the evaporator
104.
[0041] As long as the pressure at the suction port of the second
compressor 105 can be increased at the time of activation of the
refrigeration cycle apparatus 100, the position of the upstream end
K1 is not limited to the position shown in FIG. 1. That is, the
position of the upstream end K1 of the first bypass passage 112 is
not specifically limited, as long as a portion from the discharge
port of the first compressor 101 to the suction port of the
expander 103 in the working fluid circuit 106 and a portion from
the outlet of the evaporator 104 to the suction port of the second
compressor 105 in the working fluid circuit 106 can be communicated
with each other. Specifically, the first bypass passage 112 may be
connected to the working fluid circuit 106 in such a way as to
communicate between the flow passage 106a connecting the discharge
port of the first compressor 101 to the inlet of the heat radiator
102, and the flow passage 106d connecting the outlet of the
evaporator 104 to the suction port of the second compressor 105.
Depending on the case, the first bypass passage 112 may be branched
from the heat radiator 102. For example, in the case where the heat
radiator 102 is composed of an upstream part and a downstream part,
the first bypass passage 112 can be easily branched from a portion
between these two parts.
[0042] The first bypass valve 113 is provided in the upstream end
section of the first bypass passage 112. The "upstream end section"
corresponds to a section defined between the upstream end K1 and
the point of L.sub.1/4 from the upstream end K1 toward the
downstream end K2, when the full length of the first bypass passage
112 is referred to as L.sub.1. However, the position of the first
bypass valve 113 is not specifically limited, and may be provided
in the downstream end section of the first bypass passage 112, for
example. The "downstream end section" corresponds to a section
defined between the downstream end K2 and the point of L.sub.1/4
from the downstream end K2 toward the upstream end K1. The first
bypass valve 113 used in Embodiment 1 is an on-off valve, though it
is not limited thereto. In the case where the first bypass valve
113 is provided at the upstream end K1 or the downstream end K2, a
three-way valve can be used as first bypass valve 113. The use of a
three-way valve is advantageous in that the number of pipe
connections can be reduced.
[0043] The refrigeration cycle apparatus 100 is further provided
with an activation assist valve 114 provided on the working fluid
circuit 106 at a point that is located between the outlet of the
evaporator 104 and the suction port of the second compressor 105,
and that is closer to the evaporator 104 than the downstream end K2
of the first bypass passage 112 is. The activation assist valve 114
controls the flow of the working fluid in the flow passage 106d. An
on-off valve can be used as the activation assist valve 114.
[0044] Upon opening the first bypass valve 113, the working fluid
in the flow passage 106b is allowed to flow directly into the
suction port of the second compressor 105 through the first bypass
passage 112. At that time, the working fluid can be prevented from
flowing, from the evaporator 104 into the second compressor 105, by
closing the activation assist valve 114.
[0045] The refrigeration cycle apparatus 100 is further provided
with a second bypass passage 110 and a second bypass valve 111. The
second bypass passage 110 is connected to the working fluid circuit
106 so as to communicate between the flow passage 106c connecting
the discharge port of the expander 103 to the inlet of the
evaporator 104, and the flow passage 106e connecting the discharge
port of the second compressor 105 to the suction port of the first
compressor 101. That is, the second bypass passage 110 bypasses the
evaporator 104 and the second compressor 105. The second bypass
valve 111 is provided on the second bypass passage 110, and
controls the flow of the working fluid in the second bypass passage
110.
[0046] The upstream end H1 of the second bypass passage 110 is
connected to the flow passage 106c, and the downstream end H2 of
the second bypass passage 110 is connected to the flow passage
106e. That is, the second bypass passage 110 is a flow passage that
allows the working fluid in the flow passage 106c to be drawn
directly into the first compressor 101, while bypassing the
evaporator 104 and the second compressor 105.
[0047] However, as long as the first compressor 101 can draw the
working fluid in the evaporator 104 at the time of activation of
the refrigeration cycle apparatus 100, the position of the upstream
end H1 is not limited to the position shown in FIG. 1. The upstream
end H1 may be positioned at any point in the zone from the
discharge port of the expander 103 to the downstream end K2 of the
first bypass passage 112. That is, the second bypass passage 110
may be connected to the working fluid circuit 106 in such a way as
to communicate between a portion from the outlet of the evaporator
104 to the downstream end K2 of the first bypass passage 112 in the
working fluid circuit 106 (a part of the flow passage 106d), and a
portion from the discharge port of the second compressor 105 to the
suction port of the first compressor 101 in the working fluid
circuit 106 (flow passage 106e). Depending on the case, the second
bypass passage 110 may be branched from the evaporator 104. For
example, in the case where the evaporator 104 is composed of an
upstream part and a downstream part, the second bypass passage 110
can be easily branched from a portion between these two parts.
[0048] The second bypass valve 111 is provided in the upstream end
section of the second bypass passage 110. The "upstream end
section" corresponds to a section defined between the upstream end
H1 and the point of L.sub.2/4 from the upstream end H1 toward the
downstream end H2, when the full length of the second bypass
passage 111 is referred to as L.sub.2. The second bypass valve 111
may be provided also in the downstream end section of the second
bypass passage 111. The "downstream end section" corresponds to a
section defined between the downstream end H2 and the point of
L.sub.2/4 from the downstream end H2 toward the upstream end H1.
Although the second bypass valve 111 used in Embodiment 1 is a
check valve, it is not limited thereto. An on-off valve or a
three-way valve may be used therefor.
[0049] When the pressure at the outlet of the second bypass valve
111 is lower than the pressure at the inlet thereof, the second
bypass valve 111 allows the working fluid in the flow passage 106c
to flow into the second bypass passage 110. That is, when the
pressure in the flow passage 106e is lower than the pressure in the
flow passages between the discharge port of the expander 103 and
the suction port of the second compressor 105 (the flow passage
106c, the evaporator 104 and the flow passage 106d), the working
fluid in the flow passage 106c is allowed to flow directly into the
suction port of the first compressor 101 through the second bypass
passage 110.
[0050] The refrigeration cycle apparatus 100 is further provided
with a controller 117 for controlling opening and closing of the
first bypass valve 113 and the activation assist valve 114. The
first bypass valve 113 and the activation assist valve 114 are
provided respectively with valve opening and closing devices 115
and 116. The valve opening and closing devices 115 and 116
typically are composed of an actuator for actuating valves such as
a solenoid, and are controlled by the controller 117. The
controller 117 typically is composed of a microcomputer. An input
apparatus 118 provided with an activation button is connected to
the controller 117. Upon input of an operation command to the
controller 117 through the input apparatus 118, a specific control
program stored in the internal memory of the controller 117 is
executed. For example, by turning on the activation button, an
activation command (activation signal) is transmitted from the
input apparatus 118 to the controller 117. In response to the
reception of the activation command, the controller 117 performs a
specific activation control to be described later with reference to
FIG. 2. Further, the controller 117 controls the operation of the
motor 101b that drives the first compressor 101.
[0051] The refrigeration cycle apparatus 100 is further provided
with an activation detector 119 for detecting that the second
compressor 105 has been activated. The activation detector 119
transmits the detection signal to the controller 117. The
controller 117 detects the activation of the second compressor 105
on the basis of the acquisition of the detection signal. A
temperature detector, a pressure detector, or the like can be used
as the activation detector 119. The temperature detector when used
as the activation detector 119, for example, includes a temperature
detecting element such as a thermocouple and a thermistor, and
detects the difference .DELTA.T between the temperature of the
working fluid to be drawn into the expander 103 and the temperature
of the working fluid discharged from the expander 103. The pressure
detector when used as the activation detector 119, for example,
includes a piezoelectric element, and detects the difference
.DELTA.P between the pressure of the working fluid to be drawn into
the expander 103 and the pressure of the working fluid discharged
from the expander 103. Further, a timer for measuring the time
elapsed from the time point of the activation of the first
compressor 101 may be provided as the activation detector 119 for
detecting the activation of the second compressor 105. Such a timer
can be provided also as a function of the controller 117. In this
case, the controller 117 itself can serve as the activation
detector 119. Furthermore, a contact or noncontact displacement
sensor for detecting the driving of the power-recovery shaft 107,
such as an encoder, may be provided as the activation detector 119
for detecting the activation of the second compressor 105.
[0052] Depending on the type of the activation detector 119, the
method for detecting that "the second compressor 105 has been
activated" differs as follows.
[0053] In the case of the temperature detector, a specific value
T.sub.1 that has been experimentally or theoretically determined is
set by the controller 117. The controller 117 detects that "the
second compressor 105 has been activated" when the temperature
difference .DELTA.T detected by the temperature detector exceeds
the specific value T.sub.1.
[0054] In the case of the pressure detector, a specific value
P.sub.1 that has been experimentally or theoretically determined is
set by the controller 117. The controller 117 detects that "the
second compressor 105 has been activated" when the pressure
difference .DELTA.P detected by the pressure detector exceeds the
specific value P.sub.1.
[0055] The following is the reason why the activation of the second
compressor 105 can be detected from the comparison between the
temperature difference .DELTA.T and the specific value T.sub.1, or
from the comparison between the pressure difference .DELTA.P and
the specific value P.sub.1. When the first compressor 101 is
activated, the working fluid discharged from the first compressor
101 is supplied to the suction port of the second compressor 105
through the first bypass passage 112. This activates the power
recovery system 108. At this time, the second compressor 105 serves
as a driving source, and therefore the power recovery system 108
starts rotating before a large temperature difference is made
between the suction temperature of the first compressor 101 and the
discharge temperature of the first compressor 101. At the time of
activation of the rotation of the power recovery system 108, the
pressure difference in the refrigeration cycle apparatus 100 has
not yet become large enough, and thus the power to rotate the power
recovery system 108 is low. Therefore, the rotation rate of the
power recovery system 108 also is low. When the rotation rate of
the power recovery system 108 is low, the rotation rate of the
expander 103 also is low. This state corresponds to the "narrow
state" in terms of the expansion valve. Accordingly, the discharge
temperature and the discharge pressure of the first compressor 101
gradually increase as well.
[0056] As the discharge temperature and the discharge pressure of
the first compressor 101 increase, the power to rotate the expander
103 and the second compressor 105 also increases, so that the
rotation rate of the power recovery system 108 becomes high. Then,
once a high rotation rate is achieved, the power recovery system
108 stably rotates under the influence of the inertial force. It is
desirable that the first bypass passage 112 is kept open until such
a stable rotation state is achieved.
[0057] On the other hand, the suction temperature of the expander
103 gradually increases from substantially the same temperature as
the outdoor air temperature at the stopped state. The discharge
temperature (or discharge pressure) of the expander 103 depends on
the suction temperature (or suction pressure) of the expander 103.
For example, supposing that the outdoor air temperature is
10.degree. C., the suction temperature, the discharge temperature,
the suction pressure and the discharge pressure of the expander 103
at the time of activation of the power recovery system 108 and in
the regular operation of the power recovery system 108 each are
shown as follows. It should be noted that the following values are
calculated with an expansion ratio=2.0.
[0058] <At the Time of Activation>
Suction temperature: 10.degree. C. Suction pressure: 5.0 MPa
Discharge temperature: -3.0.degree. C. Discharge pressure: 3.2 MPa
Difference between suction temperature and discharge temperature:
13.degree. C. Difference between suction pressure and discharge
pressure: 1.8 MPa
<In Regular Operation>
[0059] Suction temperature: 40.degree. C. Suction pressure: 10.0
MPa Discharge temperature: 13.4.degree. C. Discharge pressure: 4.9
MPa Difference between suction temperature and discharge
temperature: 26.6.degree. C. Difference between suction pressure
and discharge pressure: 5.1 MPa
[0060] When the power recovery system 108 is activated in the state
where the discharge temperature and the discharge pressure of the
first compressor 101 are low, the suction temperature of the
expander 103 and the discharge temperature of the expander 103 each
gradually increase, as mentioned above. The difference between the
suction temperature and the discharge temperature also gradually
grows. This also can be applied to the pressure. Therefore, it is
possible to detect the activation of the second compressor 105 (the
activation of the power recovery system 108) by setting appropriate
values as the specific values T.sub.1 and P.sub.1 (for example,
slightly larger values than the temperature difference and the
pressure difference at the time of activation).
[0061] It also is possible to detect the activation of the second
compressor 105 on the basis of the discharge temperature of the
expander 103 or the discharge pressure of the expander 103, instead
of the temperature difference .DELTA. and the pressure difference
.DELTA.T. When the power recovery system 108 is activated, the
expander 103 also rotates. After drawing the working fluid, the
expander 103 expands the drawn working fluid and discharges it.
Therefore, the working fluid discharged from the expander 103 has
lower temperature and pressure than before being drawn thereinto.
It is possible to determine that the second compressor 105 has been
activated, by capturing a sudden change in the temperature (or
pressure) as well as monitoring the temperature (or pressure) at
the discharge port of the expander 103 in chronological terms.
[0062] In the case of using a timer, a specific time t that has
been experimentally or theoretically determined is set by the
controller 117. The controller 117 transmits a control signal to
the motor 101b of the first compressor 101 and starts measuring the
time by the timer. The controller 117 detects that "the second
compressor 105 has been activated" when the time measured by the
timer exceeds the specific time t.
[0063] The "specific time t" is written in the activation control
program to be executed in the controller 117. For example, the time
from the time point of the activation of the first compressor 101
to the activation of the second compressor 105 is actually measured
under various operational conditions (such as outdoor air
temperature). Then, the time from which the activation of the
second compressor 105 is determinable in all the operational
conditions can be set as the "specific time t". Theoretically, a
model of the refrigeration cycle apparatus 100 is constructed, and
a pressure difference that is necessary and sufficient to activate
the power recovery system 108 is estimated by computer simulation.
Then, using parameters such as the volume of the first compressor
101 and the filling amount of the working fluid in the working
fluid circuit 106, the initial activation time necessary to produce
the estimated pressure difference is calculated. The calculated
initial activation time can be set as the "specific time t".
[0064] <Operation of Refrigeration Cycle Apparatus 100>
[0065] FIG. 2 is a flow chart of the activation control of the
refrigeration cycle apparatus 100. The refrigeration cycle
apparatus 100 starts the regular operation after performing the
activation control shown in FIG. 2. In an operation standby state,
the first compressor 101 is stopped, the first bypass valve 113 is
closed, and the activation assist valve 114 is opened. Thus, the
pressure of the working fluid in the working fluid circuit 106 is
substantially uniform. A fan or a pump for causing a fluid (air or
water) that should exchange heat with the working fluid to flow
into the heat radiator 102 is actuated after the completion of the
activation control. Similarly, a fan or a pump for causing a fluid
that should exchange heat with the working fluid to flow into the
evaporator 104 also is actuated after the completion of the
activation control.
[0066] In step S11, in response to the reception of the activation
command from the input apparatus 118, the controller 117 transmits
a control signal to the valve opening and closing devices 115 and
116 so that the first bypass valve 113 is opened and the activation
assist valve 114 is closed (step S12). This allows the first bypass
passage 112 to be opened, and the flow passage 106d to be closed
between the outlet of the evaporator 104 and the downstream end K2
of the first bypass passage 112.
[0067] Subsequently, the controller 117 starts supplying power to
the motor 101b so that the first compressor 101 is activated (step
S13). This allows the working fluid in the flow passage 106e and
the second bypass passage 110 to be drawn into the first compressor
101. Here, instead of opening the first bypass valve 113 before the
activation of the first compressor 101, it also is possible to open
the first bypass valve 113 in response to the activation of the
first compressor 101. Similarly, in response to the activation of
the first compressor 101, the activation assist valve 114 may be
closed. That is, there is no problem as long as the working fluid
is allowed to flow in the first bypass passage 112 after the
activation of the first compressor 101 and before the rotation of
the power-recovery shaft 107.
[0068] Once the first compressor 101 starts drawing the working
fluid, the pressure in the flow passage 106e and the second bypass
passage 110 decreases. This causes the second bypass valve 111 to
be opened, so that the working fluid on the upstream side of the
second bypass valve 111, that is, the working fluid in the flow
passages from the discharge port of the expander 103 to the
activation assist valve 114 (the flow passage 106c, the evaporator
104 and a part of the flow passage 106d) flows into the second
bypass passage 110. The working fluid that has flown into the
second bypass passage 110 is drawn into the first compressor 101 to
be compressed therein, and discharged into the flow passage 106a.
Accordingly, the pressure in the flow passages from the discharge
port of the expander 103 to the activation assist valve 114 (the
flow passage 106c, the evaporator 104 and a part of the flow
passage 106d) decreases.
[0069] On the other hand, once the first compressor 101 is
activated, the pressure in the flow passages from the discharge
port of the first compressor 101 to the suction port of the
expander 103 (the flow passage 106a, the heat radiator 102 and the
flow passage 106b) increases. The compressed working fluid flows
also into the flow passage 106d between the activation assist valve
114 and the suction port of the second compressor 105 through the
first bypass passage 112. This causes the pressure in the flow
passage from the activation assist valve 114 to the suction port of
the second compressor 105 (a part of the flow passage 106d) to
increase.
[0070] As a result, as shown in FIG. 6A, the pressure at the
suction port of each of the expander 103 and the second compressor
105 is rendered relatively high, and the pressure at the discharge
port of each of the expander 103 and the second compressor 105 is
rendered relatively low. That is, a pressure difference can be
caused not only between the suction port and the discharge port of
the expander 103, but also between the suction port and the
discharge port of the second compressor 105. The pressure
difference of the working fluid acts on each of the expander 103
and the second compressor 105, and thus self-activation of the
power recovery system 108 can be easily achieved.
[0071] Upon detecting the activation of the second compressor 105
through the activation detector 119 (step S14), the controller 117
transmits a control signal to the valve opening and closing devices
115 and 116 so that the first bypass valve 113 is closed and the
activation assist valve 114 is opened (step S15). Specifically, the
controller 117 detects the activation of the second compressor 105
by receiving the detection signal from the activation detector 119,
and thereafter closes the first bypass valve 113 and opens the
activation assist valve 114. This allows the first bypass passage
112 to be closed, and the flow passage 106d to be opened. After the
completion of the activation control, the refrigeration cycle
apparatus 100 is transferred to the regular operation in which the
working fluid is circulated in the working fluid circuit 106.
[0072] In the transfer to the regular operation, the pressure at
the downstream end H2 of the second bypass passage 110 exceeds the
pressure at the upstream end H1 thereof due to the increase of the
pressure in the second compressor 105. Therefore, the second bypass
valve 111 serving as a check valve is closed. The pressure in the
flow passage 106e and the second bypass passage 110 on the
downstream side of the second bypass valve 111 is higher than the
pressure in the flow passage 106c, the evaporator 104 and the flow
passage 106d, and thus the second bypass valve 111 is kept closed.
This allows the working fluid to be circulated in the working fluid
circuit 106 during the regular operation.
[0073] It should be noted that the working fluid in the liquid
phase might be drawn into the second compressor 105 at the time of
activation of the refrigeration cycle apparatus 100, though it
depends also on the conditions such as outdoor air temperature.
Therefore, the fluid pressure motor compressor described above can
be used suitably as the second compressor 105. This is because the
fluid pressure motor compressor allows substantially no volume
change of the working fluid to be caused in the working chamber and
therefore is capable of accepting the working fluid in a liquid
phase to be drawn therein to some extent.
[0074] Further, when the first compressor 101 draws the working
fluid in the regular operation, a pressure pulsation might occur in
the flow passage 106e on the basis that the working fluid is
confined in the compression mechanism 101a. According to Embodiment
1, a part of the second bypass passage 110 (the part from the
second bypass valve 111 to the downstream end H2) can function as a
buffer space to allow the volume of the flow passage 106e to
extend. Therefore, the pulse width of the pressure pulsation that
has occurred in the flow passage 106e can be expected to be
reduced, resulting in an enhancement in the operational reliability
of the refrigeration cycle apparatus 100.
[0075] Similarly, when the second compressor 105 draws the working
fluid, a pressure pulsation might occur in the flow passage 106d on
the basis that the working fluid is confined in the working chamber
of the second compressor 105. According to Embodiment 1, a part of
the first bypass passage 112 (the part from the first bypass valve
113 to the downstream end K2) can function as a buffer space to
allow the volume of the flow passage 106d to extend. Therefore, the
pulse width of the pressure pulsation that has occurred in the flow
passage 106d can be expected to be reduced, resulting in an
enhancement in the operational reliability of the refrigeration
cycle apparatus 100.
[0076] In order to stop the operation of the refrigeration cycle
apparatus 100, the rotation rate of the first compressor 101 is
progressively reduced, for example. After the first compressor 101
is stopped, the working fluid travels through the first compressor
101, the expander 103 and the second compressor 105, taking
sufficient time. Therefore, the pressure difference in the working
fluid circuit 106 naturally disappears, so that the pressure
becomes substantially uniform to be stabilized. This allows the
expander 103 and the second compressor 105 to be stopped
naturally.
[0077] <Effects of the Refrigeration Cycle Apparatus 100>
[0078] At the time of activation of the refrigeration cycle
apparatus 100, the first bypass valve 113 is opened, and the
activation assist valve 114 is closed, according to Embodiment 1.
Therefore, the working fluid in the flow passages from the
discharge port of the first compressor 101 to the suction port of
the expander 103 can be supplied to the suction port of the second
compressor 105 through the first bypass passage 112. This causes
the pressure at the suction port of the second compressor 105 to
increase. Further, the working fluid in the flow passages from the
discharge port of the expander 103 to the activation assist valve
114 can be supplied directly to the first compressor 101 through
the second bypass passage 110 in addition to the working fluid in
the flow passage 106e.
[0079] On the other hand, once the first compressor 101 starts
drawing the working fluid, the pressure in the flow passage 106e
and the second bypass passage 110 on the downstream side of the
second bypass valve 111 decreases. This allows the second bypass
valve 111 serving as a check valve to be opened. The working fluid
in the flow passages from the discharge port of the expander 103 to
the activation assist valve 114 flows into the second bypass
passage 110, and is drawn into the first compressor 101 together
with the working fluid in the second bypass passage 110 and the
flow passage 106e.
[0080] As described above, according to the refrigeration cycle
apparatus 100, a pressure difference can be caused not only between
the suction port and the discharge port of the expander 103 but
also between the suction port and the discharge port of the second
compressor 105. Therefore, the power recovery system 108 can be
activated stably and surely, resulting in an improvement in the
reliability of the refrigeration cycle apparatus 100.
Embodiment 2
<Configuration of Refrigeration Cycle Apparatus 200>
[0081] FIG. 3 is a configuration diagram of a refrigeration cycle
apparatus 200 in Embodiment 2 of the present invention. As shown in
FIG. 3, the refrigeration cycle apparatus 200 differs from
Embodiment 1 in that a three-way valve is used as the first bypass
valve 201. That is, the first bypass valve 201 functions both as
the first bypass valve 113 and the activation assist valve 114 in
Embodiment 1. In Embodiment 2, common parts with Embodiment 1 are
designated with identical reference numerals, and the detailed
description thereof is omitted.
[0082] In Embodiment 2, the first bypass valve 201 is provided at
the junction of the downstream end K2 of the first bypass passage
112 and the flow passage 106d. This makes it possible to open and
close the first bypass passage 112 and to open and close the flow
passage 106d with one valve, easily and conveniently. Specifically,
the channel for the working fluid can be switched easily and
conveniently between (a) the state where the flow passage 106d is
opened, and the first bypass passage 112 is closed (for example, in
the regular operation), and (b) the state where the first bypass
passage 112 is opened, and the flow passage 106d is closed at the
junction with the downstream end K2 of the first bypass passage 112
(for example, in the activation control). Thus, the configuration
of the refrigeration cycle apparatus 200 can be simplified in
Embodiment 2. The first bypass valve 201 may be provided at the
junction of the upstream end K1 of the first bypass passage 112 and
the flow passage 106b.
[0083] A valve switching device 202 is provided in the first bypass
valve 201. The valve switching device 202 is typically composed of
an actuator such as a solenoid, and controlled by the controller
117.
[0084] <Operation of Refrigeration Cycle Apparatus 200>
[0085] FIG. 4 is a flow chart of the activation control of the
refrigeration cycle apparatus 200. The refrigeration cycle
apparatus 200 starts the regular operation after performing the
activation control shown in FIG. 4. In an operation standby state,
the first compressor 101 is stopped, the flow passage 106d is
opened by the first bypass valve 201, and the first bypass passage
112 is closed (the above state (a)). The pressure of the working
fluid in the working fluid circuit 106 is substantially
uniform.
[0086] In step S21, in response to the reception of the activation
command from the input apparatus 118, the controller 117 transmits
a control signal to a valve control device 202 so that the state is
switched from the above-described state (a) to the state (b) (step
S22).
[0087] Subsequently, the controller 117 starts supplying power to
the motor 101b so that the first compressor 101 is activated (step
S23). This allows the working fluid in the flow passage 106e and
the second bypass passage 110 to be drawn into the first compressor
101. The process of step S22 may be carried out in response to the
activation of the first compressor 101.
[0088] Once the first compressor 101 starts drawing the working
fluid, the pressure in the flow passage 106e and the second bypass
passage 110 decreases. This causes the second bypass valve 111 to
be opened, so that the working fluid on the upstream side of the
second bypass valve 111, that is, the working fluid in the flow
passages from the discharge port of the expander 103 to the first
bypass valve 201 (the flow passage 106c, the evaporator 104 and a
part of the flow passage 106d) flows into the second bypass passage
110. The working fluid that has flown into the second bypass
passage 110 is drawn into the first compressor 101 to be compressed
therein, and discharged into the flow passage 106a. Accordingly,
the pressure in the flow passages from the discharge port of the
expander 103 to the first bypass valve 201 (the flow passage 106c,
the evaporator 104, a part of the flow passage 106d) also
decreases.
[0089] On the other hand, once the first compressor 101 is
activated, the pressure in the flow passages from the discharge
port of the first compressor 101 to the suction port of the
expander 103 (the flow passage 106a, the heat radiator 102 and the
flow passage 106b) increases. The compressed working fluid flows
also into the flow passage 106d between the first bypass valve 201
and the suction port of the second compressor 105 through the first
bypass passage 112. This causes the pressure in the flow passage
from the first bypass valve 201 to the suction port of the second
compressor 105 (a part of the flow passage 106d) to increase. As is
the case of Embodiment 1, the state shown in FIG. 6A is
established, and thus self-activation of the power recovery system
108 can be easily achieved.
[0090] Upon detecting the activation of the second compressor 105
through the activation detector 119 (step S24), the controller 117
transmits a control signal to the valve switching device 202 so
that the state is switched from the above-described state (b) to
the state (a) (step S25). This causes the first bypass valve 201 to
be switched, and the first bypass passage 112 to be closed. After
the completion of the activation control, the refrigeration cycle
apparatus 200 is transferred to the regular operation.
[0091] Also in Embodiment 2, a part of the second bypass passage
110 (the part from the second bypass valve 111 to the downstream
end H2) can function as a buffer space to allow the volume of the
flow passage 106e to extend. Accordingly, as has been described in
Embodiment 1, the pulse width of the pressure pulsation that has
occurred in the flow passage 106e can be expected to be reduced,
resulting in an enhancement in the operational reliability of the
refrigeration cycle apparatus 200.
[0092] Similarly, the first bypass passage 112 can function as a
buffer space to allow the volume of the flow passage 106b to
extend. Accordingly, the pulse width of the pressure pulsation that
has occurred in the flow passage 106b can be expected to be
reduced, resulting in an enhancement in the operational reliability
of the refrigeration cycle apparatus 200.
[0093] <Effects of Refrigeration Cycle Apparatus 200>
[0094] At the time of activation of the refrigeration cycle
apparatus 200, the first bypass passage 112 is opened, and the flow
passage 106d is closed at the junction with the downstream end K2
of the first bypass passage 112, according to Embodiment 2.
Therefore, the working fluid in the flow passages from the
discharge port of the first compressor 101 to the suction port of
the expander 103 can be supplied to the suction port of the second
compressor 105 through the first bypass passage 112. This causes
the pressure at the suction port of the second compressor 105 to
increase. Further, the working fluid in the flow passages from the
discharge port of the expander 103 to the first bypass valve 201
can be supplied directly to the first compressor 101 through the
second bypass passage 110 in addition to the working fluid in the
flow passage 106e.
[0095] On the other hand, once the first compressor 101 starts
drawing the working fluid, the pressure in the flow passage 106e
and the second bypass passage 110 on the downstream side of the
second bypass valve 111 decreases. This allows the second bypass
valve 111 serving as a check valve to be opened. The working fluid
in the flow passages from the discharge port of the expander 103 to
the first bypass valve 201 flows into the second bypass passage
110, and is drawn into the first compressor 101 together with the
working fluid in the second bypass passage 110 and the flow passage
106e.
[0096] Furthermore, according to the refrigeration cycle apparatus
200, the pressure loss of the working fluid due to the evaporator
104 and the second compressor 105 can be avoided, and the pressure
decrease of the working fluid to be drawn by the first compressor
101 can be suppressed, at the time of activation. These allow a
reduction in the power required to increase the pressure of the
working fluid by the first compressor 101.
[0097] As described above, according to the refrigeration cycle
apparatus 200, a pressure difference can be caused not only between
the suction port and the discharge port of the expander 103 but
also between the suction port and the discharge port of the second
compressor 105. Therefore, the power recovery system 108 can be
activated stably and surely, resulting in an improvement in the
reliability of the refrigeration cycle apparatus 200.
Embodiment 3
[0098] Embodiments 1 and 2 are provided with the second bypass
passage 110 and the second bypass valve 111. However, these are not
always necessary. That is, a refrigeration cycle apparatus 300 with
a configuration in which the second bypass passage 110 and the
second bypass valve 111 are omitted can be proposed, as shown in
FIG. 5.
[0099] According to the refrigeration cycle apparatus 300, the
first bypass valve 113 is opened, and the activation assist valve
114 is closed, at the time of activation. In the state where the
power recovery system 108 has not been activated, the first
compressor 101 can draw only the working fluid in the flow passage
106e. That is, focusing on the amount of the working fluid that the
first compressor 101 can draw thereinto, Embodiment 3 may be less
advantageous than Embodiments 1 and 2. However, according also to
Embodiment 3, a pressure difference can be caused not only between
the suction port and the discharge port of the expander 103 but
also between the suction port and the discharge port of the second
compressor 105 (see FIG. 6A). Accordingly, even if the second
bypass passage 110 and the second bypass valve 111 are omitted, the
power recovery system 108 can be activated easily and surely.
[0100] Furthermore, it also is possible to omit the activation
assist valve 114 in the refrigeration cycle apparatus 300. In that
case, a pressure difference is caused only between the suction port
and the discharge port of the second compressor 105, as shown in
FIG. 6B. However, in the case where the volume of the second
compressor 105 is sufficiently larger than the volume of the
expander 103, the driving resistance of the second compressor 105
is relatively larger than the driving resistance of the expander
103. Accordingly, the state shown in FIG. 6B is more advantageous
for the activation of the power recovery system 108 than the state
shown in FIG. 10.
Reference Example
[0101] A refrigeration cycle apparatus 400 shown in FIG. 7 differs
from the conventional refrigeration cycle apparatus 500 (see FIG.
9) in the position of the upstream end H1 of the bypass passage
110. Specifically, the upstream end H1 of the bypass passage 110 is
positioned on the flow passage 106c connecting the discharge port
of the expander 103 to the inlet of the evaporator 104. Except
that, the refrigeration cycle apparatus 400 has the same
configuration including the method for detecting the activation as
the refrigeration cycle apparatus 100 that has been described with
reference to FIG. 1, etc.
[0102] According to the refrigeration cycle apparatus 400, as the
refrigeration cycle apparatus 500 that has been described with
reference to FIG. 9, a pressure difference cannot be caused between
the suction port and the discharge port of the second compressor
105. However, the refrigeration cycle apparatus 400 allows the
following advantageous effects to be obtained on the basis of the
difference in the position of the upstream end H1 of the bypass
passage 110. That is, according to the refrigeration cycle
apparatus 400, the pressure loss of the working fluid due to the
evaporator 104 and the second compressor 105 can be avoided during
a constant period before and after the activation, and thereby the
pressure decrease of the working fluid to be drawn by the first
compressor 101 can be suppressed. These result in a reduction in
the power required for the first compressor 101 to increase the
pressure of the working fluid, thus making it easy to form a stable
operation state more rapidly.
[0103] As shown in FIG. 8A, the working fluid in the liquid phase
tends to be retained in a comparatively downstream portion inside
the evaporator 4 in the state where the conventional refrigeration
cycle apparatus 500 (FIG. 9) is stopped. This can be seen also from
the Mollier diagram of FIG. 10. If the refrigeration cycle
apparatus 500 is activated in the state where the working fluid in
the liquid phase is retained inside the evaporator 4, the working
fluid in the vapor phase inside the flow passages 10c and 10d, and
the working fluid in the vapor phase inside the evaporator 4
proceed in the first compressor 1 or the second compressor 5, while
passing through the inside of the evaporator 4. Since the working
fluid travels a comparatively long distance, the pressure loss also
is comparatively large. Furthermore, there is a possibility that
the working fluid in the liquid phase is drawn into the first
compressor 101, and there also is a possibility that the working
fluid in the liquid phase serves as a resistance and increases the
pressure loss.
[0104] In contrast, according to the refrigeration cycle apparatus
400 of Reference Example, the working fluid in the vapor phase
flows back in the evaporator 104, and is drawn directly into the
first compressor 101 through the bypass passage 110, as shown in
FIG. 8. The working fluid in the liquid phase travels inside the
evaporator 104 while being vaporized, and is drawn into the first
compressor 101 through the bypass passage 110. Thus, the pressure
in the evaporator 104, that is, the suction pressure of the first
compressor 101 is maintained substantially constant. The working
fluid in the liquid phase never serves as a resistance, and the
pressure loss of the working fluid in the vapor phase is
comparatively low. Moreover, the possibility that the working fluid
in the liquid phase is drawn into the first compressor 101 at the
time of activation is low, and therefore stable activation can be
achieved.
[0105] The refrigeration cycle apparatus 100 and 200 of Embodiments
1 and 2 also are provided with the bypass passage 110, and
therefore the above-mentioned effects can be obtained at the time
of activation.
INDUSTRIAL APPLICABILITY
[0106] The refrigeration cycle apparatus of the present invention
is useful as equipments such as water heaters, air conditioners,
dryers, etc.
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