US20110023533A1

US20110023533A1 - Refrigerating cycle device

Info

Publication number: US20110023533A1
Application number: US12/921,848
Authority: US
Inventors: Yusuke Shimazu
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2008-05-22
Filing date: 2009-03-31
Publication date: 2011-02-03
Also published as: JPWO2009142067A1; WO2009142067A1; CN102016444A; CN102016444B; EP2306120A1; EP2306120A4; EP2306120B1; JP4906962B2

Abstract

Provided is a refrigerating cycle apparatus in which, even if large power is required to start up an expander, the expander may be started up by activating a compressor. An air conditioner including a first compressor for compressing a refrigerant, an outdoor heat exchanger for radiating heat of the refrigerant compressed by the first compressor, an expander for decompressing the refrigerant that has passed through the outdoor heat exchanger, an indoor heat exchanger in which the refrigerant decompressed by the expander is evaporated, and a drive shaft for recovering power that is generated when the refrigerant is decompressed by the expander includes an on-off valve which is provided between the expander and the indoor heat exchanger and controls movement of the refrigerant from the expander to the indoor heat exchanger. After the first compressor is started up to increase a pressure of the refrigerant in the expander to a critical pressure or higher, the on-off valve is opened and the expander is started up by a dynamic pressure of the refrigerant.

Description

TECHNICAL FIELD

The present invention relates to a refrigerating cycle apparatus including a power recovery device for recovering power that is generated when a refrigerant is decompressed by an expander.

BACKGROUND ART

Conventionally, there is known a refrigerating cycle apparatus including a first compressor for compressing a refrigerant, a radiator for radiating heat of the refrigerant compressed by the first compressor, an expander for decompressing the refrigerant that has passed through the radiator, an evaporator in which the refrigerant decompressed by the expander is evaporated, and a power generator which is connected to the expander, recovers power that is generated when the refrigerant is decompressed by the expander, and converts the power into electricity (see, for example, Patent Document 1).
There is also known a refrigerating cycle apparatus further including a second compressor which is provided to the expander and utilizes the power recovered from the expander.
Patent Document 1: JP 2006-132818 A

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

However, in the above-mentioned cases, when the refrigerating cycle apparatus has been in an inactive state for a longtime, for example, refrigerator oil in the expander is increased in viscosity due to low temperature so that large power is required to start up the expander. Therefore, there has been a problem in that, even when the first compressor is started up, the expander may not be able to be started up.
There has been another problem in that, when foreign particles enter from an inlet of the refrigerant of the expander or the second compressor and caught up in a rotating part therein, the operation continues under inertia of the rotating part in a steady operating state, but the expander stops in a start-up operating state because there is no inertia of the rotating part.
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is therefore to provide a refrigerating cycle apparatus in which, even if large power is required to start up an expander, the expander may be started up by activating a first compressor.

Means for Solving the Problems

The present invention provides a refrigerating cycle apparatus including: a first compressor for compressing a refrigerant; a radiator for radiating heat of the refrigerant compressed by the first compressor; an expander for decompressing the refrigerant that has passed through the radiator; an evaporator in which the refrigerant decompressed by the expander is evaporated; and a power recovery device which is connected to the expander and recovers power that is generated when the refrigerant is decompressed by the expander, the refrigerating cycle apparatus including refrigerant movement control means which is provided in a channel of the refrigerant from the expander to the evaporator and controls a flow rate of the refrigerant moving from the expander to the evaporator, in which, after the first compressor is started up to increase a pressure of the refrigerant in the expander, the refrigerant movement control means controls the flow rate of the refrigerant to start up the expander by a dynamic pressure of the refrigerant.

EFFECTS OF THE INVENTION

According to the refrigerating cycle apparatus of the present invention, even if large power is required to start up the expander, the first compressor is started up to increase the pressure of the refrigerant in the expander, and then the refrigerant movement control means controls the flow rate of the refrigerant so that the expander may be started up by the dynamic pressure of the refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A refrigerant circuit diagram in cooling operation of an air conditioner according to a first embodiment of the present invention.

[FIG. 2] A refrigerant circuit diagram in heating operation of the air conditioner of FIG. 1.

[FIG. 3] FIG. 3( a) is a schematic diagram illustrating a breakdown of power transferred from an expander to a second compressor in a steady state, and FIG. 3( b) is a schematic diagram illustrating a breakdown of the power transferred from the expander to the second compressor during activation.

[FIG. 4] FIG. 4( a) is a diagram illustrating a pressure of a refrigerant, a volume of the refrigerant, and a mass of the refrigerant in the steady state of the expander, and FIG. 4( b) is a diagram illustrating the pressure of the refrigerant, the volume of the refrigerant, and the mass of the refrigerant during the activation of the expander.

[FIG. 5] A flow chart illustrating start-up operation of the air conditioner of FIGS. 1 and 2.

[FIG. 6] A refrigerant circuit diagram of the air conditioner in a second start-up mode.

[FIG. 7] A refrigerant circuit diagram of a water heater according to a second embodiment of the present invention.

[FIG. 8] A flow chart illustrating start-up operation of the water heater of FIG. 7.

[FIG. 9] A refrigerant circuit diagram of a water heater according to a third embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention are described with reference to drawings. Throughout the drawings, the same reference symbols are assigned to the same or like members and parts for description.

First Embodiment

FIG. 1 is a refrigerant circuit diagram in cooling operation of an air conditioner according to a first embodiment of the present invention, and FIG. 2 is a refrigerant circuit diagram in heating operation of the air conditioner of FIG. 1.
The air conditioner, which is a refrigerating cycle apparatus according to this embodiment, includes a first compressor 1 for compressing a refrigerant, an outdoor heat exchanger 2 which serves as a radiator in which the refrigerant radiates heat in the cooling operation and as an evaporator in which the refrigerant is evaporated in the heating operation, an expander 3 for decompressing the refrigerant passing therethrough, an indoor heat exchanger 4 which serves as an evaporator in which the refrigerant is evaporated in the cooling operation and as a radiator in which the refrigerant radiates heat in the heating operation, and a drive shaft 5 which is connected to the expander 3 and serves as a power recovery device for recovering power that is generated when the refrigerant is decompressed by the expander 3.
The air conditioner also includes an on-off valve 6 which is provided downstream of the expander 3 and serves as refrigerant movement control means that is fully closed to restrict movement of the refrigerant from the expander 3 to the downstream side and is fully opened to control a flow rate of the refrigerant moving from the expander 3 to the downstream side.
Further, the air conditioner uses carbon dioxide as the refrigerant. The carbon dioxide refrigerant has an ozone depletion potential of zero and a smaller global warming potential compared to the conventional fluorocarbon refrigerant.
The outdoor heat exchanger 2 includes a first outdoor heat exchanger portion 2 a and a second outdoor heat exchanger portion 2 b. In a channel of the refrigerant between the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b, there are provided a switch 7 a and a switch 7 b which are closed in the cooling operation to block the refrigerant and opened in the heating operation to allow the refrigerant to pass therethrough.
Therefore, the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b are configured so that the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b are connected in series in the cooling operation and the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b are connected in parallel in the heating operation.
The indoor heat exchanger 4 includes a first indoor heat exchanger portion 4 a and a second indoor heat exchanger portion 4 b, and the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b are connected in parallel.
The first indoor heat exchanger portion 4 a is connected to an indoor expansion valve 8 a, and the second indoor heat exchanger portion 4 b is connected to an indoor expansion valve 8 b.
Therefore, the refrigerant is decompressed in the cooling operation so that the refrigerant may be evaporated in the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b, and the refrigerant is decompressed in the heating operation so that the refrigerant, which has radiated heat in the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b, may be evaporated in the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b.
In the channel of the refrigerant between the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b, there is provided a second compressor 9 for compressing the refrigerant that has passed through the first outdoor heat exchanger portion 2 a in the cooling operation.
The second compressor 9 is connected to the expander 3 through the drive shaft 5, and hence the power generated in the expander 3 is recovered by the drive shaft 5 and transferred to the second compressor 9.
In the channel of the refrigerant between the first compressor 1 and the first outdoor heat exchanger portion 2 a and the channel of the refrigerant between the first outdoor heat exchanger portion 2 a and the second compressor 9, there are provided a switch 10 a and a switch 10 b which are opened in the cooling operation to allow the refrigerant to pass therethrough and closed in the heating operation to block the refrigerant, respectively.
In the channel of the refrigerant between the first compressor 1 and the second compressor 9, there is provided a switch 7 c which is closed in the cooling operation to block the refrigerant and allows the refrigerant to pass therethrough in the heating operation.
At an inlet of the refrigerant of the expander 3, there is provided a first foreign particle trap 11 for trapping foreign particles contained in the refrigerant that flows into the expander 3.
At an inlet of the refrigerant of the second compressor 9, there is provided a second foreign particle trap 12 for trapping foreign particles contained in the refrigerant that flows into the second compressor 9.
Each of the first foreign particle trap 11 and the second foreign particle trap 12 includes a strainer made of a coarse metal mesh. The coarseness of the metal mesh determines the size of the smallest foreign particles to be trapped.
The size of the smallest foreign particles to be trapped by the first foreign particle trap 11 is set to be smaller than the largest gap in an expansion chamber of the expander 3.
The size of the smallest foreign particles to be trapped by the second foreign particle trap 12 is set to be smaller than the largest gap in a compression chamber of the second compressor 9.
The size of the smallest foreign particles to be trapped by each of the first foreign particle trap 11 and the second foreign particle trap 12 is 0.5 mm. Therefore, a pressure loss caused by each of the first foreign particle trap 11 and the second foreign particle trap 12 is decreased, to thereby suppress a reduction of power to be recovered.
At an inlet of the refrigerant of the first compressor 1, there is provided an accumulator 13 for accumulating the refrigerant before flowing into the first compressor 1.
In the channel of the refrigerant among the outdoor heat exchanger 2, the second compressor 9, the indoor heat exchanger 4, and the accumulator 13, there is provided a first four-way valve 14. Valves in the first four-way valve 14 are switched so that the refrigerant is allowed to flow from the second compressor 9 to the second outdoor heat exchanger portion 2 b and the refrigerant is allowed to flow from the indoor heat exchanger 4 to the accumulator 13 in the cooling operation, and the refrigerant is allowed to flow from the second compressor 9 and a check valve 15 bypassing the second compressor 9 and the second foreign particle trap 12 to the indoor heat exchanger 4 and the refrigerant is allowed to flow from the outdoor heat exchanger 2 to the accumulator 13 in the heating operation. It should be noted that the check valve 15 may be included in the second compressor 9.
In the channel of the refrigerant among the outdoor heat exchanger 2, the expander 3, and the indoor heat exchanger 4, there is provided a second four-way valve 16. Valves in the second four-way valve 16 are switched so that the refrigerant is allowed to flow from the second outdoor heat exchanger portion 2 b through the expander 3 to the indoor heat exchanger 4 in the cooling operation, and the refrigerant is allowed to flow from the indoor heat exchanger 4 through the expander 3 to the outdoor heat exchanger 2 in the heating operation.
The first four-way valve 14 and the second four-way valve 16 serve to allow the refrigerant to pass through the expander 3 and the second compressor 9 in the same direction regardless of the cooling operation or the heating operation.
In the channel of the refrigerant between the outdoor heat exchanger 2 and the indoor heat exchanger 4, there are provided a bypass circuit 17 for bypassing the second four-way valve 16, the expander 3, and the on-off valve 6, and a bypass valve 18 for adjusting the flow rate of the refrigerant passing through the bypass circuit 17.
In the channel of the refrigerant between the second four-way valve 16 and the first foreign particle trap 11, there is provided a pre-expansion valve 19 for adjusting the flow rate of the refrigerant moving from the second four-way valve 16 to the first foreign particle trap 11.
The bypass valve 18 and the pre-expansion valve 19 are adjusted so that the flow rate of the refrigerant passing through the second compressor 9 and the sum of the flow rates of the refrigerant passing through the expander 3 and the bypass circuit 17 are equal.
This way, a pressure on the high-pressure side may be increased to a desirable pressure to be adjusted, and further the power generated in the expander 3 may be recovered. Therefore, the refrigerating cycle may be maintained in a highly efficient state.
It should be noted that, without limiting to adjusting the bypass valve 18 and the pre-expansion valve 19, any other method may be used to adjust the flow rate of the refrigerant passing through the second compressor 9 and the flow rates of the refrigerant passing through the expander 3 and the bypass circuit 17 to be equal.
At an outlet of the refrigerant of the first compressor 1, there is provided a pressure sensor 20 a for measuring a pressure of the refrigerant that flows out of the first compressor 1. At the inlet of the refrigerant of the expander 3, there is provided a pressure sensor 20 b for measuring the pressure of the refrigerant that flows into the expander 3. At an outlet of the refrigerant of the on-off valve 6, there is provided a pressure sensor 20 c for measuring the pressure of the refrigerant that flows out of the on-off valve 6.
It should be noted that, without limiting to those positions, the pressure sensor 20 a, the pressure sensor 20 b, and the pressure sensor 20 c may be located at any positions as long as the pressure of the refrigerant that flows out of the first compressor 1, the pressure of the refrigerant that flows into the expander 3, and the pressure of the refrigerant that flows out of the on-off valve 6 may be measured, respectively.
Further, each of the pressure sensor 20 a, the pressure sensor 20 b, and the pressure sensor 20 c may be a temperature sensor for measuring a temperature of the refrigerant as long as the pressure may be estimated.
The pressure sensor 20 a, the pressure sensor 20 b, and the pressure sensor 20 c are connected to a controller 21. The controller 21 controls the opening and closing of the on-off valve 6, the bypass valve 18, and the pre-expansion valve 19 based on values of the pressure of the refrigerant measured by the pressure sensor 20 a, the pressure sensor 20 b, and the pressure sensor 20 c.
The controller 21 includes judging means (not shown) for judging, after the on-off valve 6 is fully opened, whether or not the expander 3 is started up, storage means (not shown) for storing the number of times it is judged that the expander 3 is not started up, and display means (not shown) for displaying, when the number of times stored in the storage means has reached a predetermined number of times, a notification that the expander 3 has failed.
The first compressor 1, the outdoor heat exchanger 2, the expander 3, the drive shaft 5, the on-off valve 6, the switch 7 a, the switch 7 b, the switch 7 c, the second compressor 9, the switch 10 a, the switch 10 b, the first foreign particle trap 11, the second foreign particle trap 12, the accumulator 13, the first four-way valve 14, the check valve 15, the second four-way valve 16, the bypass circuit 17, the bypass valve 18, the pre-expansion valve 19, the pressure sensor 20 a, the pressure sensor 20 b, the pressure sensor 20 c, and the controller 21 constitute an outdoor unit 22.
The first indoor heat exchanger portion 4 a and the indoor expansion valve 8 a constitute an indoor unit 23 a, and the second indoor heat exchanger portion 4 b and the indoor expansion valve 8 b constitute an indoor unit 23 b.
The outdoor unit 22 is connected to one end of each of a liquid main pipe 24 and a gas main pipe 25, the other end of the liquid main pipe 24 is connected to one end of each of a liquid branch pipe 26 a and a liquid branch pipe 26 b, and the other end of the gas main pipe 25 is connected to one end of each of a gas branch pipe 27 a and a gas branch pipe 27 b.
The other end of the liquid branch pipe 26 a is connected to the indoor expansion valve 8 a, and the other end of the liquid branch pipe 26 b is connected to the indoor expansion valve 8 b.
The other end of the gas branch pipe 27 a is connected to the first indoor heat exchanger portion 4 a, and the other end of the gas branch pipe 27 b is connected to the second indoor heat exchanger portion 4 b.
The first compressor 1 is connected to a motor (not shown). The first compressor 1 is driven by the motor to operate.
The expander 3 and the second compressor 9 are of a positive displacement type, specifically, a scroll type.
It should be noted that, without limiting to the scroll type, the expander 3 and the second compressor 9 may be of any other positive displacement type.
The expander 3 and the second compressor 9 do not have a motor that generates heat.
Further, the expander 3 and the second compressor 9 have substantially equal bearing loads, and hence the expander 3 and the second compressor 9 cause small loss.
Therefore, there is no need to use the refrigerant to cool inside the expander 3 and the second compressor 9, and hence decrease of refrigerator oil that occurs when the refrigerant cools the expander 3 and the second compressor 9 may be suppressed.
As a result, reliability of the expander 3 and the second compressor 9 may be increased.
Further, reduction in heat transfer performance of the heat exchanger due to the decrease of the refrigerator oil may be suppressed.
The first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b may be connected via the channel of the refrigerant in series in the cooling operation to improve the heat transfer performance for radiating heat, and in parallel in the heating operation to reduce the pressure loss.
Next, operation of the air conditioner according to this embodiment is described.
In the cooling operation, the refrigerant of low pressure first flows into the first compressor 1 and is compressed to become high in temperature and medium in pressure.
After flowing out of the first compressor 1, the refrigerant passes through the switch 10 a and flows into the first outdoor heat exchanger portion 2 a of the outdoor heat exchanger 2.
After radiating heat to transfer the heat to outdoor air in the first outdoor heat exchanger portion 2 a, the refrigerant becomes low in temperature and medium in pressure.
After flowing out of the first outdoor heat exchanger portion 2 a, the refrigerant flows into the second compressor 9 and is compressed to become high in temperature and high in pressure.
After flowing out of the second compressor 9, the refrigerant passes through the first four-way valve 14 and flows into the second outdoor heat exchanger portion 2 b, in which the refrigerant radiates heat to transfer the heat to outdoor air and become low in temperature and high in pressure.
After flowing out of the second outdoor heat exchanger portion 2 b, the refrigerant is branched to a path that leads to the second four-way valve 16 and a path that leads to the bypass valve 18.
The refrigerant that has passed through the second four-way valve 16 passes through the pre-expansion valve 19 and the first foreign particle trap 11, flows into the expander 3, and is decompressed to become low in pressure and take on a state of low dryness.
At this time, power is generated in the expander 3 upon the decompression of the refrigerant. The power is recovered by the drive shaft 5 and transferred to the second compressor 9 to be used by the second compressor 9 to compress the refrigerant.
After flowing out of the expander 3, the refrigerant passes through the on-off valve 6 and the second four-way valve 16, and then joins the refrigerant that has been directed to the bypass valve 18 and has passed through the bypass circuit 17. The refrigerant flows out of the outdoor unit 22, passes through the liquid main pipe 24 and then the liquid branch pipe 26 a and the liquid branch pipe 26 b, and flows into the indoor unit 23 a and the indoor unit 23 b, in which the refrigerant flows into the indoor expansion valve 8 a and the indoor expansion valve 8 b.
In the indoor expansion valve 8 a and the indoor expansion valve 8 b, the refrigerant is further decompressed.
After flowing out of the indoor expansion valve 8 a and the indoor expansion valve 8 b, the refrigerant absorbs heat from indoor air and is evaporated in the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b to take on a state of high dryness while maintaining low pressure.
This way, indoor air is cooled.
After flowing out of the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b, the refrigerant flows out of the indoor unit 23 a and the indoor unit 23 b, passes through the gas branch pipe 27 a and the gas branch pipe 27 b and then the gas main pipe 25, and flows into the outdoor unit 22, in which the refrigerant passes through the first four-way valve 14 and flows into the accumulator 13 and again into the first compressor 1.
The above-mentioned operation is repeated to transfer heat of indoor air to outdoor air and thereby cool the room.
In the heating operation, the refrigerant of low pressure first flows into the first compressor 1 and is compressed to become high in temperature and high in pressure.
After flowing out of the first compressor 1, the refrigerant passes through the switch 7 c, the check valve 15, and the first four-way valve 14.
At this time, part of the refrigerant, which has passed through the switch 7 c, passes through the second compressor 9 and then joins the refrigerant that has passed through the check valve 15 to flow into the first four-way valve 14.
After passing through the first four-way valve 14, the refrigerant flows out of the outdoor unit 22, passes through the gas main pipe 25 and then the gas branch pipe 27 a and the gas branch pipe 27 b, and flows into the indoor unit 23 a and the indoor unit 23 b, in which the refrigerant flows into the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b of the indoor heat exchanger 4. In the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b, the refrigerant radiates heat to transfer the heat to indoor air to become low in temperature and high in pressure.
After flowing out of the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b, the refrigerant is decompressed in the indoor expansion valve 8 a and the indoor expansion valve 8 b.
After flowing out of the indoor expansion valve 8 a and the indoor expansion valve 8 b, the refrigerant flows out of the indoor unit 23 a and the indoor unit 23 b, passes through the liquid branch pipe 26 a and the liquid branch pipe 26 b and then the liquid main pipe 24, flows into the outdoor unit 22, and is branched to a path that leads to the second four-way valve 16 and a path that leads to the bypass valve 18.
The refrigerant that has passed through the second four-way valve 16 passes through the pre-expansion valve 19 and the first foreign particle trap 11, flows into the expander 3, and is decompressed to become low in pressure and take on the state of low dryness.
At this time, power is generated in the expander 3 upon the decompression of the refrigerant. The power is recovered by the drive shaft 5, transferred to the second compressor 9, and used by the second compressor 9 to compress the refrigerant.
After flowing out of the expander 3, the refrigerant passes through the on-off valve 6 and the second four-way valve 16, and then joins the refrigerant that has been directed to the bypass valve 18 and has passed the bypass circuit 17. The refrigerant is branched again to flow into the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b.
In the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b, the refrigerant absorbs heat from outdoor air and is evaporated to take on a state of high dryness while maintaining low pressure.
After flowing out of the first outdoor heat exchanger portion 2 a and the second outdoor heat exchanger portion 2 b, the refrigerant joins again, passes through the first four-way valve 14, and flows into the accumulator 13 and again into the first compressor 1.
The above-mentioned operation is repeated to transfer heat of outdoor air to indoor air and thereby heat the room.
The air conditioner is used as a multi-system air conditioner for a building and adapted to increase an operation efficiency in a mild cooling season in which a cooling load is not large in order to increase an annual operation efficiency.
Therefore, the expander 3, the second compressor 9, the outdoor heat exchanger 2, and the indoor heat exchanger 4 are designed to be best for the mild cooling season. In the heating operation, it is more advantageous in control for the refrigerant not to pass through the expander 3 and the second compressor 9.
However, when the refrigerant does not pass through the expander 3 and the second compressor 9 in the heating operation, the refrigerant dwells in the expander 3 and the second compressor 9. As a result, when the expander 3 and the second compressor 9 are started up, the expander 3 and the second compressor 9 may be damaged due to poor lubrication.
Therefore, the refrigerant is allowed to pass through the expander 3 and the second compressor 9 also in the heating operation.
It should be noted that the second compressor 9 operates to such an extent as not to compress the refrigerant.
Next, power to be transferred from the expander 3 to the second compressor 9 of the air conditioner according to this embodiment is described.
FIG. 3( a) is a schematic diagram illustrating a breakdown of the power transferred from the expander 3 to the second compressor 9 in a steady state, and FIG. 3( b) is a schematic diagram illustrating a breakdown of the power transferred from the expander 3 to the second compressor 9 during activation.
Both in the steady state and during the activation, the power to be ultimately recovered is power obtained by subtracting the loss caused by the expander 3 and the loss caused by the second compressor 9 from the power received by the expander 3 from the dynamic pressure of the refrigerant.
However, in comparison to the steady state, the loss generated by the expander 3 and the loss generated by the second compressor 9 become larger during the activation, and hence less power is ultimately recovered.
This is because, soon after the activation of the expander 3 when the number of rotations is equal to or less than a predetermined number of rotations, a friction coefficient of the bearing is increased to increase the friction loss.
Further, when the expander 3 is in an inactive state, static friction larger than dynamic friction occurs in bearings of the expander 3 and the second compressor 9 to further increase the loss caused by the expander 3 and the loss caused by the second compressor 9.
Further, when the air conditioner has been in an inactive state for a long time, the refrigerator oil in the expander 3 and the second compressor 9 is increased in viscosity due to low temperature. When the air conditioner is to be started up to start up the expander 3 from this state, the loss caused by the expander 3 and the loss caused by the second compressor 9 are further increased.
Further, soon after the air conditioner is manufactured and shipped, the operation time is too short for slide members of the expander 3 and the second compressor 9 to fit well, to thereby cause large friction and further increase the loss caused by the expander 3 and the loss caused by the second compressor 9.
Next, operation of the expander 3 during the activation, that is, soon after the on-off valve 6 is fully opened from a fully closed state, is described.
FIG. 4( a) is a diagram illustrating the pressure of the refrigerant, a volume of the refrigerant, and a mass of the refrigerant in the steady state of the expander 3, and FIG. 4( b) is a diagram illustrating the pressure of the refrigerant, the volume of the refrigerant, and the mass of the refrigerant during the activation of the expander 3.
In the steady state, the pressure of the refrigerant in the expansion chamber of the expander 3 is equal to an inlet pressure that is the pressure at the inlet of the refrigerant of the expander 3 at a start point of an expansion process, decreases in the course of the expansion process from the start point to an end point of the expansion process, and becomes equal to an outlet pressure that is the pressure at an outlet of the refrigerant of the expander 3 at the end point of the expansion process.
The volume of the refrigerant in the expansion chamber of the expander 3 increases from the start point to the end point of the expansion process.
The mass of the refrigerant in the expansion chamber of the expander 3 does not change between the start point and the end point of the expansion process.
In contrast, during the activation, that is, soon after the on-off valve 6 is fully opened from the fully closed state, the pressure of the refrigerant in the expansion chamber of the expander 3 does not change between the start point and the end point of the expansion process. On the downstream side of the end point, the pressure changes discontinuously to be decreased and become equal to the pressure of the refrigerant measured by the pressure sensor 20 c.
The volume of the refrigerant in the expansion chamber of the expander 3 increases as in the steady state from the start point to the end point of the expansion process.
The mass of the refrigerant in the expansion chamber of the expander 3 increases from the start point to the end point of the expansion process.
Therefore, the circulating volume of the refrigerant during the period in which the expander 3 is started up and the expander 3 is rotated once is larger than the circulating volume of the refrigerant in the steady state to give larger rotation power.
Further, the interface area between the expansion chamber and space after the expansion process is large before and after the endpoint of the expansion process, and a pressure difference between before and after the end point of the expansion process is larger than the pressure difference in the steady state soon after the on-off valve 6 is fully opened from the fully closed state, to thereby give large recovered power that is determined by the area and the pressure.
As described above, soon after the on-off valve 6 is fully opened from the fully closed state, the expander 3 may obtain the large recovered power.
Therefore, even when the loss caused by the expander 3 and the loss caused by the second compressor 9 are large, the expander 3 may be started up.
Further, the on-off valve 6 is fully closed from when the first compressor 1 is started up until when the pressure of the refrigerant in the expander 3 becomes a critical pressure or higher, and hence the high-pressure refrigerant reduces the viscosity of the refrigerator oil in the expander 3 and the second compressor 9.
This way, the loss caused by the expander 3 and the loss caused by the second compressor 9 soon after the on-off valve 6 is fully opened may be decreased, and hence the expander 3 may obtain the large recovered power.
Next, start-up operation of the air conditioner according to this embodiment is described.
FIG. 5 is a flow chart illustrating the start-up operation of the air conditioner of FIGS. 1 and 2.
When the air conditioner is started up (Step S1), it is judged which of cooling operation and heating operation the requested operation is (Step S2).
When it is judged in Step S2 that the heating operation is requested, the heating operation is started (Step S3).
On the other hand, when it is judged in Step S2 that the cooling operation is requested, the cooling operation is started (Step S4).
When the cooling operation is started, a first cooling circuit is set, in which the switch 7 a, the switch 7 b, and the switch 7 c are closed, the switch 10 a and the switch 10 b are opened, valves in the first four-way valve 14 are switched so that the refrigerant is allowed to flow from the second compressor 9 to the second outdoor heat exchanger portion 2 b and the refrigerant is allowed to flow from the indoor heat exchanger 4 to the accumulator 13, and valves in the second four-way valve 16 are switched so that the refrigerant is allowed to flow from the second outdoor heat exchanger portion 2 b through the expander 3 to the indoor heat exchanger 4 (Step S5).
Then, the on-off valve 6 is fully closed and the pre-expansion valve 19 is fully opened (Step S6), and other devices are put into a first initial cooling setting that is an initial state of the cooling operation (Step S7) so that the air conditioner enters a first start-up mode (Step S8).
When the air conditioner enters the first start-up mode, first, the first compressor 1 is started up (Step S9), the pressure sensor 20 b measures the pressure of the refrigerant at the inlet of the expander 3, the pressure sensor 20 c measures the pressure of the refrigerant at the outlet of the on-off valve 6, and the controller 21 calculates a difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the on-off valve 6 (Step S10).
Then, the controller 21 judges whether a predetermined period Ta has elapsed since the first compressor 1 is started up (Step S11).
The predetermined period Ta is preset in a range of from 10 seconds to 60 seconds.
It should be noted that the predetermined period Ta is not limited to the time range.
When the controller 21 judges in Step S11 that the predetermined period Ta has not elapsed since the first compressor 1 is started up, the process returns to Step S10.
On the other hand, when the controller 21 judges in Step S11 that the predetermined period Ta has elapsed, it is judged whether the pressure of the refrigerant at the inlet of the expander 3 is equal to or higher than the critical pressure and the difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the on-off valve 6 is equal to or larger than a predetermined pressure Pa (Step S12).
The predetermined pressure Pa is preset in a range of from 2.5 MPa to 5 MPa.
When the controller 21 judges in Step S12 that the pressure of the refrigerant at the inlet of the expander 3 is not equal to or higher than the critical pressure or that the difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the on-off valve 6 is not equal to or larger than the predetermined pressure Pa, a degree of opening of the bypass valve 18 is reduced (Step S13) and the process returns to Step S10.
On the other hand, when the controller 21 judges in Step S12 that the pressure of the refrigerant at the inlet of the expander 3 is equal to or higher than the critical pressure and that the difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the on-off valve 6 is equal to or larger than the predetermined pressure Pa, the on-off valve 6 is fully opened (Step S14).
Then, the controller 21 judges whether a predetermined period Tb has elapsed since the on-off valve 6 is fully opened (Step S15).
The predetermined period Tb is shorter than the predetermined period Ta of Step S11 and preset in a range of from 5 seconds to 30 seconds.
It should be noted that the predetermined period Tb is not limited to the time range.
When the controller 21 judges in Step S15 that the predetermined period Tb has not elapsed since the on-off valve 6 is fully opened, Step S15 is repeated.
On the other hand, when the controller 21 judges in Step S15 that the predetermined period Tb has elapsed, the pressure sensor 20 a measures the pressure of the refrigerant at the outlet of the first compressor 1, the pressure sensor 20 b measures the pressure of the refrigerant at the inlet of the expander 3, and the controller 21 calculates a difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the first compressor 1 (Step S16).
Then, the controller 21 judges whether the difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the first compressor 1 is equal to or larger than a predetermined pressure Pb (Step S17).
The predetermined pressure Pb is preset in a range of from 0 MPa to 0.5 MPa.
It should be noted that the predetermined pressure Pb is not limited to the pressure range.
When the controller 21 judges in Step S17 that the difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the first compressor 1 is equal to or larger than the predetermined pressure Pb, the judging means judges that the expander 3 has successfully started up, the air conditioner exits the first start-up mode, and first steady control in a steady state is performed (Step S18).
On the other hand, when the controller 21 judges in Step S17 that the difference between the pressure of the refrigerant at the inlet of the expander 3 and the pressure of the refrigerant at the outlet of the first compressor 1 is not equal to or larger than the predetermined pressure Pb, the judging means judges that the activation of the expander 3 has failed, and the air conditioner enters a backup mode (Step S19).
When the air conditioner enters the backup mode, the storage means adds one to the number of times the activation failed stored therein (Step S20), and further judges whether the number of times the activation failed is the predetermined number of times (Step S21).
The predetermined number of times is preset in a range of from 5 to 10.
It should be noted that the predetermined number of times is not limited to the number range.
When the controller 21 judges in Step S21 that the number of times the activation failed is less than the predetermined number of times, the process returns to Step S5.
On the other hand, when the controller 21 judges in Step S21 that the number of times the activation failed has reached the predetermined number of times, the expander 3 or the second compressor 9 is regarded as having failed, and the air conditioner starts backup control (Step S22).
In the backup control, first, the first compressor 1 is stopped (Step S23), the display means of the controller 21 displays a notification that the expander 3 or the second compressor 9 has failed (Step S24) to notify the manager or the user of the failure.
Then, a second cooling circuit is set so that the refrigerant does not flow into the expander 3 and the second compressor 9 (Step S25), in which the on-off valve 6 is fully closed, the pre-expansion valve 19 is closed, and the bypass valve 18 is opened so that the refrigerant does not pass through the expander 3 and the second compressor 9, and other actuators are put into a second initial cooling setting that is a state before cooling is started (Step S26).
The air conditioner enters a second start-up mode in which the expander 3 is not started up (Step S27), and the first compressor 1 is started up without operating the expander 3 to perform steady operation in the steady state (Step S28), so that the cooling operation in which the refrigerant is circulated continues as illustrated in a refrigerant circuit diagram of FIG. 6.
In this case, if, for example, the expander 3 or the second compressor 9 has failed, the refrigerant does not pass through the expander 3 and the second compressor 9 so as to prevent the first compressor 1, the indoor expansion valve 8 a, the indoor expansion valve 8 b, and the like from being damaged.
Further, if, for example, the expander 3 or the second compressor 9 has failed, the cooling operation may be continued.
As described above, according to the air conditioner of this embodiment, even if large power is required to start up the expander 3, the on-off valve 6 is fully opened after the first compressor 1 is started up and the pressure of the refrigerant in the expander 3 is increased, to thereby increase the refrigerant that passes through the on-off valve 6. As a result, the expander 3 may be started up by the dynamic pressure of the refrigerant.
Further, even if the refrigerator oil in the expander 3 and the second compressor 9 is increased in viscosity due to low temperature, when the pressure of the refrigerant at the inlet of the expander 3 is equal to or higher than the critical pressure, the on-off valve 6 is fully opened to allow the refrigerant to pass through the on-off valve 6. The refrigerant of the critical pressure or higher acts on the refrigerator oil to decrease the viscosity of the refrigerator oil. Therefore, the losses caused by the expander 3 and the second compressor 9 may be decreased.
Further, when the difference between the pressure of the refrigerant at the inlet of the refrigerant of the expander 3 and the pressure of the refrigerant at the outlet thereof is equal to or larger than the predetermined pressure, the on-off valve 6 is fully opened to allow the refrigerant to pass through the on-off valve 6. Therefore, the expander 3 may be started up by the high dynamic pressure of the refrigerant.
Further, the air conditioner of this embodiment includes the judging means for judging whether or not the expander 3 is started up after the on-off valve 6 is fully opened, the storage means for storing the number of times the judging means judges that the expander 3 is not started up, and a display device for displaying a notification that the expander 3 and the second compressor 9 have failed when the number of times stored in the storage means has reached the predetermined number of times. Therefore, the manager or the user may easily notice that the expander 3 and the second compressor 9 have failed.
In the channel of the refrigerant between the outdoor heat exchanger 2 and the indoor heat exchanger 4, there are provided the bypass circuit 17 connected in parallel to the expander 3 and the on-off valve 6 that are connected in series, and the bypass valve 18 for adjusting the flow rate of the refrigerant passing through the bypass circuit 17. When the number of times stored in the storage means has reached the predetermined number of times, the refrigerant passes through the bypass circuit 17. Therefore, when the expander 3 or the second compressor 9 fails and hence the expander 3 and the second compressor 9 do not work, the refrigerant may circulate through the channel of the refrigerant between the outdoor heat exchanger 2 and the indoor heat exchanger 4.
Further, the refrigerant movement control means is the on-off valve 6 that is fully closed to restrict the movement of the refrigerant from the expander 3 to the indoor heat exchanger 4 in the cooling operation and is fully opened to control the flow rate of the refrigerant that moves from the expander 3 to the indoor heat exchanger 4 in the cooling operation. Therefore, the movement of the refrigerant from the expander 3 to the indoor heat exchanger 4 may be controlled with a simple configuration.
Further, in the channel of the refrigerant between the first compressor 1 and the outdoor heat exchanger 2, there is provided the second compressor 9, and power is transferred from the expander 3 via the drive shaft 5 to the second compressor 9 in the cooling operation. Therefore, the power that is generated when the refrigerant is decompressed by the expander 3 may be used by the second compressor 9, so that the air conditioner may be increased in efficiency.
Further, at the inlet of the refrigerant of the expander 3, there is provided the first foreign particle trap 11 for trapping the foreign particles entering the expander 3. The size of the smallest foreign particles to be trapped by the first foreign particle trap 11 is smaller than the largest gap in the expansion chamber of the expander 3. Therefore, the foreign particles may be prevented from entering the expander 3 and causing the expander 3 to fail.
Further, at the inlet of the refrigerant of the second compressor 9, there is provided the second foreign particle trap 12 for trapping the foreign particles entering the second compressor 9. The size of the smallest foreign particles to be trapped by the second foreign particle trap 12 is smaller than the largest gap in the compression chamber of the second compressor 9. Therefore, the foreign particles may be prevented from entering the second compressor 9 and causing the second compressor 9 to fail.
The refrigerant is carbon dioxide and hence may reduce ozone depletion and global warming compared to the conventional fluorocarbon refrigerant.
It should be noted that, in this embodiment, the indoor heat exchanger 4 has been described to include the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b. However, it should be understood that the present invention is not limited thereto, and the indoor heat exchanger 4 may include one indoor heat exchanger portion, or the indoor heat exchanger 4 may include three or more indoor heat exchanger portions.
Further, the air conditioner has been described to have the configuration in which the indoor expansion valve 8 a is connected to the first indoor heat exchanger portion 4 a and the indoor expansion valve 8 b is connected to the second indoor heat exchanger portion 4 b. However, the air conditioner may have a configuration in which a single indoor expansion valve is connected to the first indoor heat exchanger portion 4 a and the second indoor heat exchanger portion 4 b, or alternatively, the air conditioner may have a configuration in which an outdoor expansion valve is provided to the outdoor unit 22.
Further, the on-off valve 6 has been described to restrict the movement of the refrigerant from the expander 3 to the downstream side when fully closed and to control the flow rate of the refrigerant moving from the expander 3 to the downstream side when fully opened. However, it should be understood that the present invention is not limited thereto, and a flow regulating valve that is fully closed or nearly fully closed to restrict the movement of the refrigerant from the expander 3 to the downstream side and is adjusted in degree of opening to control the flow rate of the refrigerant moving from the expander 3 to the downstream side may be used.
Further, the second compressor 9 has been described to operate only on the rotation power transferred from the expander 3. However, it should be understood that the present invention is not limited thereto, and the second compressor 9 may operate, for example, on the rotation power transferred from the expander 3 as well as the rotation power from a motor.
Further, whether or not to start up the expander 3 has been judged based on the difference between the pressure of the refrigerant at the inlet of the refrigerant of the expander 3 and the pressure of the refrigerant at the outlet of the refrigerant of the on-off valve 6. However, it should be understood that the present invention is not limited thereto, and whether or not to start up the expander 3 may be judged by installing a tachometer or a vibrometer to the expander 3 and the second compressor 9 or by measuring the temperature of the refrigerant at the outlet of the refrigerant of or inside the second compressor 9.

Second Embodiment

FIG. 7 is a refrigerant circuit diagram of a water heater according to a second embodiment of the present invention.
The water heater, which is a refrigerating cycle apparatus according to this embodiment, includes a compressor 28 for compressing a refrigerant, a radiator 29 for radiating heat of the refrigerant compressed by the compressor 28 to heat water, an expander 30 for decompressing the refrigerant that has passed through the radiator 29, an evaporator 31 in which the refrigerant that has passed through the expander 30 absorbs heat and is evaporated, and a power generator 32 which is connected to the expander 30 and serves as a power recovery device for recovering power that is generated when the refrigerant is decompressed by the expander 30.
In a channel of the refrigerant between the expander 30 and the evaporator 31, there is provided an opening regulating valve 33 which serves as refrigerant movement control means that is fully closed or nearly fully closed to restrict the movement of the refrigerant from the expander 30 to the evaporator 31 and is adjusted in degree of opening to control the flow rate of the refrigerant moving from the expander 30 to the evaporator 31.
At an inlet of the refrigerant of the compressor 28, there is provided a pressure sensor 34 a for measuring a pressure of the refrigerant that flows into the compressor 28. At an outlet of the refrigerant of the compressor 28, there is provided a pressure sensor 34 b for measuring the pressure of the refrigerant that flows out of the compressor 28.
The pressure sensor 34 a and the pressure sensor 34 b are connected to a controller 35. The controller 35 adjusts the degree of opening of the opening regulating valve 33 based on values of the pressure of the refrigerant measured by the pressure sensor 34 a and the pressure sensor 34 b.
The controller 35 includes judging means (not shown) for judging, after the degree of opening of the opening regulating valve 33 is increased, whether or not the expander 30 is started up, and storage means (not shown) for storing the number of times it is judged that the expander 30 is not started up.
The refrigerant is made of carbon dioxide.
The radiator 29 includes water transportation means 36 for pumping water into the radiator 29 and a hot water supply tank 37 for storing water that has been heated by passing through the radiator 29.
The evaporator 31 includes a blower (not shown) for blowing on the evaporator 31.
Next, operation of the water heater according to this embodiment is described.
First, the refrigerant of low temperature and low pressure flows into the compressor 28 and is compressed to take on a state of high temperature and high pressure.
After flowing out of the compressor 28, the refrigerant radiates heat in the radiator 29 to take on a state of low temperature and high pressure.
At this time, the heat of the refrigerant is transferred to water via the radiator 29 to heat the water.
After flowing out of the radiator 29, the refrigerant is decompressed in the expander 30 to take on a state of low temperature and low pressure.
At this time, power that is generated when the refrigerant is decompressed in the expander 30 is recovered by the power generator 32.
The power recovered from the power generator 32 is converted to electrical energy and used by the compressor 28, the water transportation means 36, and the blower.
After flowing out of the expander 30, the refrigerant absorbs heat in the evaporator 31 and is evaporated to become low in pressure and change from a state of low dryness to a state of high dryness.
At this time, the blower blows on the evaporator 31 so that the refrigerant in the evaporator 31 may absorb the heat effectively.
After flowing out of the evaporator 31, the refrigerant flows into the compressor 28 again.
Next, start-up operation of the water heater according to this embodiment is described.
FIG. 8 is a flow chart illustrating the start-up operation of the water heater of FIG. 7.
When the water heater is started up (Step S101), the opening regulating valve 33 is switched to a state of being fully opened or nearly fully opened (Step S102).
Next, other devices are set to an initial operating state (Step S103), and the water heater enters a start-up mode to start up the compressor 28 (Step S104).
Next, the pressure sensor 34 a and the pressure sensor 34 b measure the pressure of the refrigerant at the inlet of the compressor 28 and the pressure of the refrigerant at the outlet thereof, respectively, and the controller 35 calculates a difference between the pressure of the refrigerant at the inlet of the compressor 28 and the pressure of the refrigerant at the outlet thereof (Step S105).
Next, the controller 35 judges whether the difference between the pressure of the refrigerant at the inlet of the compressor 28 and the pressure of the refrigerant at the outlet thereof is equal to or larger than the predetermined pressure (Step S106).
When the controller 35 judges in Step S106 that the difference between the pressure of the refrigerant at the inlet of the compressor 28 and the pressure of the refrigerant at the outlet thereof is smaller than the predetermined pressure, the process returns to Step S105.
On the other hand, when the controller 35 judges in Step S106 that the difference between the pressure of the refrigerant at the inlet of the compressor 28 and the pressure of the refrigerant at the outlet thereof is equal to or larger than the predetermined pressure, the degree of opening of the opening regulating valve 33 is increased (Step S107).
Next, the controller 35 judges whether a predetermined period has elapsed since the degree of opening of the opening regulating valve 33 is increased (Step S108).
When the controller 35 judges in Step S108 that the predetermined period has not elapsed since the degree of opening of the opening regulating valve 33 is increased, Step S108 is repeated.
On the other hand, when the controller 35 judges in Step S108 that the predetermined period has elapsed, a voltage of the power generator 32 is measured (Step S109).
Then, the controller 35 judges whether the voltage of the power generator 32 is equal to or higher than a predetermined voltage (Step S110).
When the controller 35 judges in Step S110 that the voltage of the power generator 32 is equal to or higher than the predetermined voltage, the judging means regards the activation of the expander 30 as a success, the water heater exits the start-up mode, and steady control in a steady state is performed (Step S111).
On the other hand, when the controller 35 judges in Step S110 that the voltage of the power generator 32 is lower than the predetermined voltage, the judging means regards the activation of the expander 30 as a failure, and the water heater enters a backup mode (Step S112).
When the water heater enters the backup mode, the storage means of the controller 35 adds one to the number of times the activation failed stored therein, and further judges whether the number of times the activation failed is equal to or more than a predetermined number of times.
When the controller 35 judges that the number of times the activation failed is less than the predetermined number of times, the process returns to Step S102.
On the other hand, when the controller 35 judges that the number of times the activation failed has reached the predetermined number of times, the expander 30 or the power generator 32 is regarded as having failed, and the water heater starts backup control (Step S113).
In the backup control, the compressor 28 is stopped.
As described above, according to the water heater of this embodiment, the power generator 32 serves as the power recovery device, and the power recovered by the power generator 32 may be converted to electrical energy and used by the compressor 28, the water transportation means 36, and the blower.
Other effects are the same as those of the first embodiment.

Third Embodiment

FIG. 9 is a refrigerant circuit diagram of a water heater according to a third embodiment of the present invention.
The water heater according to this embodiment includes a first compressor 38 for compressing a refrigerant, a radiator 29 for radiating heat of the refrigerant compressed by the first compressor 38, an expander 30 for decompressing the refrigerant that has passed through the radiator 29, an evaporator 31 in which the refrigerant that has passed through the expander 30 absorbs heat and is evaporated, a drive shaft 39 which is connected to the expander 30 and serves as a power recovery device for recovering power that is generated when the refrigerant is decompressed by the expander 30, and a second compressor 40 which is connected to the drive shaft 39 and compresses the refrigerant that flows from the evaporator 31 into the first compressor 38.
Other configurations are the same as those of the second embodiment.
Next, operation of the water heater according to this embodiment is described.
The refrigerant of low temperature and low pressure first flows into the second compressor 40 and is compressed to take on a state of high temperature and medium pressure.
After flowing out of the second compressor 40, the refrigerant flows into the first compressor 38 and is compressed to take on a state of high temperature and high pressure.
After flowing out of the first compressor 38, the refrigerant radiates heat in the radiator 29 to take on a state of low temperature and high pressure.
At this time, the heat of the refrigerant is transferred to water via the radiator 29 to heat the water.
After flowing out of the radiator 29, the refrigerant is decompressed in the expander 30 to take on a state of low temperature and low pressure.
At this time, power that is generated when the refrigerant is decompressed in the expander 30 is recovered by the drive shaft 39 and used by the second compressor 40.
After flowing out of the expander 30, the refrigerant absorbs heat in the evaporator 31 and is evaporated to become low in pressure and change from a state of low dryness to a state of high dryness.
At this time, the blower blows on the evaporator 31 so that the refrigerant in the evaporator 31 may absorb the heat effectively.
After flowing out of the evaporator 31, the refrigerant flows into the second compressor 40 again.
As described above, according to the water heater of this embodiment, the second compressor 40 is provided in a channel of the refrigerant between the evaporator 31 and the first compressor 38, and the drive shaft 39 is connected between the expander 30 and the second compressor 40. Therefore, the power that is generated when the refrigerant is decompressed in the expander 30 may be used by the second compressor 40.
Other effects are the same as those of the first embodiment.

Claims

1. A refrigerating cycle apparatus including:

a first compressor for compressing a refrigerant;

a radiator for radiating heat of the refrigerant compressed by the first compressor;

an expander for decompressing the refrigerant that has passed through the radiator;

an evaporator in which the refrigerant decompressed by the expander is evaporated; and

a power recovery device which is connected to the expander and recovers power that is generated when the refrigerant is decompressed by the expander,

the refrigerating cycle apparatus comprising refrigerant movement control means which is provided in a channel of the refrigerant from the expander to the evaporator and controls a flow rate of the refrigerant moving from the expander to the evaporator,

wherein, after the first compressor is started up to increase a pressure of the refrigerant in the expander, the refrigerant movement control means controls the flow rate of the refrigerant to start up the expander by a dynamic pressure of the refrigerant in the expander.

2. A refrigerating cycle apparatus according to claim 1, wherein the refrigerant movement control means controls the flow rate of the refrigerant when the pressure of the refrigerant at an inlet of the refrigerant of the expander is equal to or higher than a critical pressure.

3. A refrigerating cycle apparatus according to claim 1, wherein the refrigerant movement control means controls the flow rate of the refrigerant when a difference between the pressure of the refrigerant at an inlet of the refrigerant of the refrigerant movement control means and the pressure of the refrigerant at an outlet thereof is equal to or larger than 2.5 MPa.

4. A refrigerating cycle apparatus according to claim 1, further comprising:

judging means for judging, after the refrigerant movement control means controls the flow rate of the refrigerant, whether or not the expander is started up;

storage means for storing a number of times the judging means judges that the expander is not started up; and

display means for displaying, when the number of times stored in the storage means has reached a predetermined number of times, a notification that the expander has failed.

5. A refrigerating cycle apparatus according to claim 4, further comprising, in a channel of the refrigerant between the radiator and the evaporator, a bypass circuit connected in parallel to the expander and the refrigerant movement control means that are connected in series, and a bypass valve for adjusting the flow rate of the refrigerant passing through the bypass circuit,

wherein the refrigerant is allowed to pass through the bypass circuit when the number of times stored in the storage means has reached the predetermined number of times.

6. A refrigerating cycle apparatus according to claim 1, wherein the refrigerant movement control means comprises an on-off valve that is fully closed to restrict movement of the refrigerant from the expander to the evaporator and is fully opened to control the flow rate of the refrigerant moving from the expander to the evaporator.

7. A refrigerating cycle apparatus according to claim 1, wherein the refrigerant movement control means comprises a flow regulating valve that is totally closed or nearly totally closed to restrict movement of the refrigerant from the expander to the evaporator and is adjusted in degree of opening to control the flow rate of the refrigerant moving from the expander to the evaporator.

8. A refrigerating cycle apparatus according to claim 1, wherein the power recovery device comprises a power generator.

9. A refrigerating cycle apparatus according to claim 1, further comprising, in a channel of the refrigerant between the first compressor and the radiator, a second compressor for compressing the refrigerant,

wherein the power recovery device comprises one drive shaft which is connected between the expander and the second compressor and transfers the power from the expander to the second compressor.

10. A refrigerating cycle apparatus according to claim 1, further comprising, in a channel of the refrigerant between the first compressor and the evaporator, a second compressor for compressing the refrigerant,

11. A refrigerating cycle apparatus according to claim 1, further comprising a first foreign particle trap for trapping foreign particles entering the expander at an inlet of the refrigerant of the expander,

wherein a size of a smallest one of the foreign particles to be trapped by the first foreign particle trap is smaller than a largest gap in an expansion chamber of the expander.

12. A refrigerating cycle apparatus according to claim 9, further comprising a second foreign particle trap for trapping foreign particles entering the second compressor at an inlet of the refrigerant of the second compressor,

wherein a size of a smallest one of the foreign particles to be trapped by the second foreign particle trap is smaller than a largest gap in a compression chamber of the second compressor.

13. A refrigerating cycle apparatus according to claim 1, wherein the refrigerant comprises carbon dioxide.