JP2002228275A - Supercritical steam compression refrigerating cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercritical steam compression refrigerating cycle capable of securing cooling capacity during high efficient operation and on a high outside air temperature condition. SOLUTION: The supercritical steam compression refrigerant cycle is provided with a gas cooler 2, a throttle valve 8, an economizer 7, an expansion valve 4, an evaporator 5, a compressor 1, and a refrigerant injection line 9 to guide a refrigerant, passing the economizer 7 reduced in a pressure by the throttle valve 8, to the middle of the suction compression of the compressor 1. A refrigerant injection line 9 is provided with an injection pressure switching means 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
₂ ) The present invention relates to a supercritical vapor compression refrigeration cycle using, for example, a refrigerant as a refrigerant, and more particularly to a technique suitable for ensuring efficient cooling and operating under conditions where the outside air temperature is high.

[0002]

2. Description of the Related Art In recent years, there has been an increasing interest in preserving the global environment. However, there is a concern that an alternative fluorocarbon such as R134a, which has been conventionally used as a refrigerant for air conditioners for vehicles, will have an effect on global warming. Have been. For this reason, as a substitute for such alternative CFC refrigerants,
Research on refrigeration cycles using substances originally present in nature, so-called natural refrigerants, has been conducted. As a candidate for such a natural refrigerant, carbon dioxide (CO ₂ ) has attracted attention. This CO ₂ not only contributes significantly less to global warming than CFC alternatives, is not flammable, and is basically harmless to the human body.

[0003] The operating principle of a vapor compression refrigeration cycle using a CO ₂ refrigerant (hereinafter abbreviated as a CO ₂ refrigeration cycle) is basically the same as that of a conventional vapor compression refrigeration cycle using a Freon refrigerant. . Therefore, FIG. 10 shows a configuration of a general CO ₂ refrigeration cycle, and FIG. 11 shows a Mollier diagram for brief description. In FIG. 10, reference numeral 1 denotes a compressor for compressing a CO ₂ refrigerant in a gaseous state, and reference numeral 2 denotes a gas cooler (2) for exchanging heat between the CO ₂ refrigerant compressed by the compressor 1 and the outside air to cool it. Radiator), 3 is gas cooler 2
A pressure (high-pressure) control valve provided on the outlet side pipe of the apparatus, 4 is an expansion valve (decompression device) for reducing the pressure of the high-pressure CO ₂ refrigerant, 5 is an evaporator (evaporator) functioning as a cooler, When the CO ₂ refrigerant in the phase state evaporates (evaporates) in the evaporator 4, it takes off latent heat of evaporation from the air and cools it.

The operation of the CO ₂ refrigeration cycle is the same as that of a conventional vapor compression refrigeration cycle using chlorofluorocarbon as a refrigerant. That is, as indicated by ABCDA in the CO ₂ Mollier diagram (see FIG. 11), the compressor 1
The CO ₂ refrigerant in the gaseous phase is compressed at (A-B), and the CO ₂ refrigerant in the gaseous state compressed at a high temperature is cooled by the gas cooler 2 (B-C). Then, the pressure is reduced by the expansion valve (C
-D) The CO ₂ refrigerant in the gas-liquid two-phase state is evaporated by the evaporator 4 (DA), and latent heat of evaporation is taken from an external fluid such as air to cool the external fluid.

However, the critical temperature of the CO ₂ refrigerant is about 31 ° C., which is considerably lower than the critical temperature of Freon, which is a conventional refrigerant. Therefore, when the outside air temperature is high, such as in summer, the temperature of the CO ₂ refrigerant on the gas cooler 2 side is reduced. It will be higher than the critical point temperature of CO ₂ . That is, on the outlet side of the gas cooler 2, there is a supercritical region where the CO ₂ refrigerant does not condense (the line segment BC does not cross the saturated liquid line SL). In the supercritical region, the high pressure at the same refrigerant temperature is undefined, and determines the high pressure (strictly, the gas cooler outlet refrigerant pressure) with respect to the refrigerant temperature, more precisely, the gas cooler outlet refrigerant temperature (outside air temperature + α ° C). There is a need.

That is, the outlet side of the gas cooler 2 (point C)
States are determined by the CO ₂ temperature at the discharge pressure and the gas cooler outlet side of the compressor 1, further, CO ₂ temperature at the gas cooler outlet side is determined by the heat transfer capability and the outside air temperature of the gas cooler 2 (uncontrollable) Therefore, the refrigerant temperature at the gas cooler outlet cannot be substantially controlled. Therefore, the state of the gas cooler outlet side (point C) can be controlled by controlling the discharge pressure of the compressor 1 (gas cooler outlet side pressure). In other words, when the outside air temperature is high, such as in summer, in order to secure a sufficient cooling capacity (enthalpy difference), the EFGGHE diagram should be used in the Mollier diagram.
As shown in the above, it is necessary to increase the pressure on the gas cooler outlet side. Therefore, the operating pressure of the compressor 1 needs to be set higher than that of a conventional refrigeration cycle using chlorofluorocarbon. Taking a vehicle air conditioner as an example, the operating pressure of the compressor 1 is 3 kg / c for a conventional R134 (Freon) refrigerant.
m ² , whereas 40 kg / CO ₂ refrigerant
cm ^2, and the shutdown pressure is R13
4 (Freon) refrigerant is about 15 kg / cm ² , whereas CO ₂ refrigerant is about 100 kg / cm ² .

As described above, in order to increase the gas cooler outlet pressure, the discharge pressure of the compressor 1 must be increased as described above, so that the compression work of the compressor 1 (the enthalpy change ΔL during the compression process) is reduced. To increase. Therefore, when the increase in the enthalpy change ΔL in the compression process (AB) is larger than the increase in the enthalpy change ΔI in the evaporation process (DA), the coefficient of performance of the CO ₂ refrigeration cycle (COP = ΔI / ΔL) worsens. The thick solid line η _max in FIG. 11 is an optimal control line obtained by calculating the CO ₂ temperature at the gas cooler outlet side and the pressure at which the coefficient of performance is maximized. In order to efficiently operate the above-described CO ₂ refrigeration cycle, It is necessary to control the gas cooler outlet side pressure and the gas cooler outlet side CO ₂ temperature as shown by the optimal control line η _max .

From the background described above, for example, Japanese Patent Application No.
No. 2570 discloses a CO ₂ refrigeration cycle using an economizer (hereinafter, referred to as an economizer cycle). In this economizer cycle, as shown in FIG. 12, the high pressure (outside air temperature + α)
A branching portion 6 for branching the CO ₂ refrigerant at (° C.) is provided, and an economizer 7 is arranged between the branching portion 6 and the expansion valve 4. The economizer 7 is a part of the C that is branched from the branch part 6 and reduced and cooled to a predetermined intermediate pressure by the throttle valve 8.
This is a counter-current heat exchanger that exchanges heat between the O ₂ refrigerant (injection refrigerant) and another high-pressure side CO ₂ refrigerant (refrigerant refrigerant) directly led from the gas cooler 2, and expands due to this heat exchange. CO ₂ supplied to the valve 4 and the evaporator 5
It is configured to lower the temperature of the refrigerant (refrigerant). The injection refrigerant cooled to the intermediate pressure passes through the refrigerant injection line 9 and the compressor 1
Is injected during the compression process.

[0009] For example, Japanese Patent Application No. 3-515570 discloses a CO ₂ refrigeration cycle (see FIG. 13) in which a countercurrent heat exchanger called an intercooler is arranged on the downstream side of the gas cooler 2. I have. The intercooler 10 has a high pressure (outside air temperature + α)
CO ₂ to the CO ₂ refrigerant ° C.) flowing out from the evaporator 5
C, which is configured to be cooled by a refrigerant and passes through the expansion valve 4 and the evaporator 5 similarly to the economizer 7 described above.
It has the function of lowering the temperature of the O ₂ refrigerant. In addition, the code | symbol 11 in a figure has shown the receiver.

[0010]

[SUMMARY OF THE INVENTION] As described above, lowering the temperature of the gas cooler outlet side refrigerant by employing an economizer and intercooler, CO ₂ which is adapted even when the outside air temperature is high to obtain a cooling capacity There is a refrigeration cycle conventionally. However, in the above-described conventional economizer cycle, since the capacity control of the economizer 7 is performed by adjusting the opening of the throttle valve 8, the intermediate pressure increases when the opening of the throttle valve 8 increases, and the intermediate pressure increases when the opening decreases. The pressure drops. For this reason, when the opening degree is increased, the temperature difference between the injection refrigerant and the high-pressure side refrigerant (refrigerant refrigerant) decreases, but the mass flow rate increases more than the reduction of the temperature difference, so that the cooling capacity of the CO ₂ refrigeration cycle increases. Conversely, if the opening is reduced, the temperature difference will increase,
The refrigeration capacity will be reduced because the mass flow rate will decrease more than the temperature difference increases. Therefore, when the opening degree is increased and the mass flow rate of the injection refrigerant is increased, the capacity of the economizer 7 is increased and the cooling capacity can be improved. However, the increase of the injection refrigerant increases the circulation flow rate of the refrigeration refrigerant passing through the evaporator 5. Therefore, there is a problem that a large increase in cooling capacity cannot be expected.

[0011] Further, CO using an intercooler 10
_{In the 2} refrigeration cycle, the CO ₂ refrigerant whose temperature has increased due to heat exchange in the intercooler 10 is sucked into the compressor 1,
The CO ₂ refrigerant having a high suction temperature is compressed by the compressor 1. For this reason, the compression efficiency of the compressor 1 becomes disadvantageous,
In addition, there has been a problem that the increase in the discharge temperature imposes a great burden on the refrigerating machine oil, the seal surface, and the like.

By the way, in the CO ₂ refrigeration cycle shown in FIG. 10, under the overload condition where the outside air temperature is as high as 55 ° C., for example, the cooling capacity (enthalpy) at the balance point (intersection with the optimum control line) where the highest COP is obtained. Difference) is further reduced. For this reason, in order to secure the refrigerating capacity, there is no other way than increasing the rotation speed of the compressor 1 and increasing the circulation amount of the CO ₂ refrigerant, and therefore, the COP is extremely poor. Also, assuming all operating conditions, under conditions where the outside air temperature is high and the inside temperature is low and the pressure ratio is high, the compressor discharge temperature will be higher than the CFC refrigerant due to the physical properties of CO ₂ , so the lubricating oil protection Therefore, injection for cooling or the like is required, and the COP is further reduced.

In a CFC-based refrigeration cycle conventionally used, a sight glass is provided at the outlet of the receiver, and the amount of the refrigerant is confirmed by the flow state of the liquid refrigerant. On the other hand, in a CO ₂ refrigeration cycle that is a supercritical cycle,
In the supercritical region, CO ₂ does not condense, and the flow in the expansion valve 4 also changes instantaneously from supercritical (gas phase) → liquid phase → two phases.
Even if the amount of O ₂ refrigerant charged changes, the optimum refrigerant amount cannot be determined in the gaseous phase, so that means for confirming the optimal refrigerant amount is desired.

As described above, the conventional supercritical vapor compression refrigeration cycle such as the above-mentioned conventional CO ₂ refrigeration cycle has problems in securing refrigeration capacity under overload conditions, high efficiency operation under a wide range of conditions, and refrigerant amount management. The present invention has been made in view of the above circumstances, and provides a supercritical vapor compression refrigeration cycle that enables refrigeration capacity to be ensured under overload conditions, high-efficiency operation under a wide range of conditions, and refrigerant amount management. is there.

[0015]

The present invention employs the following means in order to solve the above-mentioned problems. The supercritical vapor compression refrigeration cycle according to claim 1, a radiator that cools the compressed refrigerant, the internal pressure of which exceeds the critical pressure of the refrigerant, and a branch portion that branches the refrigerant flowing out of the radiator, A first decompression device that decompresses one of the refrigerants branched at the branch portion to a first predetermined pressure, and heat-exchanges the refrigerant depressurized by the first decompression device with the refrigerant on the other side, and An economizer for cooling the refrigerant, a second decompression device for depressurizing the other side of the refrigerant cooled by the economizer to a second predetermined pressure lower than the first predetermined pressure, and a second decompression device. An evaporator for evaporating the refrigerant, and a compression device that absorbs and compresses the refrigerant flowing out of the evaporator and discharges the refrigerant toward the radiator, wherein the refrigerant decompressed by the first decompression device is provided by the compression device. To guide in the middle of the suction compression process A supercritical vapor compression refrigeration cycle including a refrigerant injection line, there shall be characterized in that a injection pressure switching means to said coolant injection line.

According to such a supercritical vapor compression refrigeration cycle, in addition to controlling the flow rate of the injection refrigerant by the first pressure reducing device, the optimum injection pressure according to the operating conditions can be selectively switched. It is possible to control the economizer performance by changing the evaporation temperature.

The supercritical vapor compression refrigeration cycle according to claim 2 is a radiator that cools the compressed refrigerant and has an internal pressure exceeding the critical pressure of the refrigerant, and a branch that branches the refrigerant flowing out of the radiator. Part, a first decompression device that decompresses one of the refrigerants branched at the branch part to a first predetermined pressure, and heat-exchanges the refrigerant depressurized by the first decompression device with the refrigerant on the other side. An economizer that cools the refrigerant on the other side, and the refrigerant on the other side cooled by the economizer,
A second decompression device for reducing the pressure to a second predetermined pressure lower than the first predetermined pressure, an evaporator for evaporating the refrigerant decompressed by the second decompression device, and a device located between the economizer and the evaporator. An intercooler that cools the refrigerant on the other side with the refrigerant flowing out of the evaporator, and absorbs and compresses the refrigerant flowing out of the evaporator through the intercooler,
A supercritical vapor compression refrigeration comprising: a compression device that discharges toward the radiator; and a refrigerant injection line that guides the refrigerant decompressed by the first decompression device to the middle of the suction compression process of the compression device. A cycle, a first on-off valve installed between the radiator and the branch portion, a second on-off valve installed between the economizer and the intercooler, and the radiator and the first on-off valve. A first bypass line, which is branched from between the valve and a second on-off valve and is connected between the second on-off valve and the intercooler, and has a third on-off valve on the way, and between the economizer and the second on-off valve. A branch is provided between the intercooler and the second pressure reducing device, and a second bypass line having a fourth on-off valve is provided on the way.

According to such a supercritical vapor compression refrigeration cycle, the first on-off valve, the second on-off valve, the third on-off valve and the fourth on-off valve
The opening / closing operation of the opening / closing valve makes it possible to selectively switch the optimum operation from the economizer alone operation, the intercooler alone operation, and the economizer / intercooler combined operation.

According to a third aspect of the present invention, there is provided a supercritical vapor compression refrigeration cycle for cooling a compressed refrigerant and branching the radiator having an internal pressure exceeding the critical pressure of the refrigerant and branching the refrigerant flowing out of the radiator. And a first decompression device that decompresses one of the refrigerants branched at the branch portion to a first predetermined pressure,
An economizer that exchanges heat between the refrigerant decompressed by the first decompression device and the refrigerant on the other side to cool the refrigerant on the other side;
A second decompression device that decompresses the refrigerant on the other side cooled by the economizer to a second predetermined pressure lower than the first predetermined pressure, and an evaporator that evaporates the refrigerant depressurized by the second decompression device. An intercooler located between the economizer and the evaporator, which cools the other side refrigerant with the refrigerant flowing out of the evaporator, and absorbs and compresses the refrigerant flowing out of the evaporator through the intercooler. And a compression device for discharging toward the radiator, and a supercritical vapor compression having a refrigerant injection line for guiding the refrigerant decompressed by the first decompression device to the middle of a suction compression process of the compression device. A refrigeration cycle, wherein an injection pressure switching means is provided in the refrigerant injection line, and a first on-off valve installed between the radiator and the branch portion A second on-off valve installed between the economizer and the intercooler, and a branch between the radiator and the first on-off valve connected to the second on-off valve and the intercooler. A first bypass line provided with a third opening / closing valve in the middle, and a branch opening from between the economizer and the second opening / closing valve, which is connected between the intercooler and the second pressure reducing device; And a second bypass line provided with a valve.

According to such a supercritical vapor compression refrigeration cycle, in addition to controlling the flow rate of the injection refrigerant by the first pressure reducing device, the optimum injection pressure according to the operating conditions can be selectively switched, so that the intermediate pressure (injection side) (Evaporation temperature) to control the economizer capacity, and furthermore, the first opening / closing valve, the second opening / closing valve, the third opening / closing valve, and the fourth opening / closing valve can be opened / closed to operate the economizer alone or intercooler alone. The optimal operation can be selectively switched from the operation and the combined operation of the economizer and the intercooler.

In the supercritical vapor compression refrigeration cycle according to claim 1 or 3, the compression device is a scroll compressor having a plurality of injection ports, and the injection pressure switching means includes a plurality of the injection lines. An on-off valve may be provided for each branch, and the branched injection lines may be connected to different injection ports, respectively, or the compression device may be a reciprocating type, and the injection pressure switching means may be provided on the injection line. The opening and closing operation timing of the opening and closing valve may be adjusted. The reciprocating compressor includes, for example, a crank type and a swash plate type. Further, in the supercritical vapor compression refrigeration cycle according to any one of claims 2 to 5, the first on-off valve, the second on-off valve, the third on-off valve, and the fourth on-off valve are opened and closed by the compression device. Preferably, the switching operation is performed by detecting the temperature of the discharged refrigerant.

According to a seventh aspect of the present invention, there is provided a supercritical vapor compression refrigeration cycle in which a compressed refrigerant is cooled, and a radiator whose internal pressure exceeds the critical pressure of the refrigerant, and a branch for branching the refrigerant flowing out of the radiator. And a first decompression device that decompresses one of the refrigerants branched at the branch portion to a first predetermined pressure,
An economizer that exchanges heat between the refrigerant decompressed by the first decompression device and the refrigerant on the other side to cool the refrigerant on the other side;
A second decompression device that decompresses the refrigerant on the other side cooled by the economizer to a second predetermined pressure lower than the first predetermined pressure, and an evaporator that evaporates the refrigerant depressurized by the second decompression device. A compression device that absorbs and compresses the refrigerant flowing out of the evaporator and discharges the refrigerant toward the radiator,
A supercritical vapor compression refrigeration cycle including a refrigerant injection line for guiding a refrigerant depressurized by the first decompression device to the middle of a suction compression process of the compression device,
The compressor may include a plurality of compressors arranged in series, and the refrigerant injection line may be connected between the plurality of compressors.

According to such a supercritical vapor compression refrigeration cycle, a multistage compression one-stage expansion type refrigeration cycle is obtained.
Since each compressor can be operated independently, refrigeration capacity and efficiency can be secured under a wide range of conditions. In this case, it is preferable to perform high-pressure control at the outlet of the economizer, and it is preferable that the plurality of compressors be independently controlled in rotation speed. In addition, suitable rotation speed control means include inverter control and pole number conversion.

According to a tenth aspect of the present invention, in the supercritical vapor compression refrigeration cycle, a radiator for cooling the compressed refrigerant and having an internal pressure exceeding the critical pressure of the refrigerant, and a refrigerant flowing out of the radiator at a predetermined pressure. A decompression device for decompressing the refrigerant, an evaporator for evaporating the refrigerant decompressed by the decompression device, and a compression device for absorbing and compressing the refrigerant flowing out of the evaporator and discharging the refrigerant toward the radiator. A critical vapor compression refrigeration cycle, comprising: means for depressurizing the refrigerant flowing out of the radiator to a liquid phase region; an intermediate pressure receiver for holding surplus refrigerant; and a visual recognition unit for judging a flow state of the liquid refrigerant. The present invention is characterized in that a refrigerant amount management means is provided.

According to such a supercritical vapor compression refrigeration cycle, the refrigerant exiting the radiator is intentionally brought into a liquid state,
Since the flow state can be visually confirmed from the visual recognition unit, it is possible to determine the optimum refrigerant amount. In this case, it is preferable that the visual recognition unit is provided at a lower portion or an outlet of the intermediate pressure receiver.

According to a twelfth aspect of the present invention, in the supercritical vapor compression refrigeration cycle, a radiator that cools the compressed refrigerant and whose internal pressure exceeds the critical pressure of the refrigerant, and a branch that branches the refrigerant flowing out of the radiator. Part, a first decompression device that decompresses one of the refrigerants branched at the branch part to a first predetermined pressure, and heat-exchanges the refrigerant depressurized by the first decompression device with the refrigerant on the other side. An economizer that cools the refrigerant on the other side, and the refrigerant on the other side cooled by the economizer,
A second decompression device for reducing the pressure to a second predetermined pressure lower than the first predetermined pressure, an evaporator for evaporating the refrigerant decompressed by the second decompression device, and absorbing and compressing the refrigerant flowing out of the evaporator, A supercritical vapor compression refrigeration comprising: a compression device that discharges toward the radiator; and a refrigerant injection line that guides the refrigerant decompressed by the first decompression device to the middle of the suction compression process of the compression device. A cycle, wherein the compressor is composed of a low-stage compressor and a high-stage compressor arranged in series, while connecting the refrigerant injection line between the low-stage compressor and the high-stage compressor,
Means for reducing the pressure of the refrigerant flowing out of the economizer to a two-phase region, an intermediate pressure receiver for holding the surplus refrigerant, and a refrigerant amount management means comprising a visual recognition unit for judging the flow state of the liquid refrigerant, A gas vent circuit is provided to connect the upper part of the intermediate pressure receiver and the suction side of the high-pressure stage compressor, and a gas-phase refrigerant is supplied from the intermediate pressure receiver in a gas-liquid two-phase region to the suction side of the high-pressure stage compressor. It is characterized in that it is configured to bleed air.

According to such a supercritical vapor compression refrigeration cycle, the inside of the intermediate pressure receiver is in a gas-liquid two-phase state, and the gas phase component of the refrigerant that does not work in the evaporator is extracted to the suction side of the high-pressure compressor. This reduces the power of the low-pressure compressor,
Efficiency can be improved. In this case, if the flow state of the liquid refrigerant component separated in the intermediate pressure receiver is checked by the visual recognition unit to determine the amount of the refrigerant, the optimum amount of the refrigerant can be easily visually determined.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a supercritical vapor compression refrigeration cycle according to the present invention will be described below with reference to the drawings. In the following embodiments, a description will be given on the assumption that the refrigerant used in the supercritical region is carbon dioxide (CO ₂ ).

<First Embodiment> In the first embodiment shown in FIG. 1, reference numeral 1 denotes a compressor, 2 denotes a gas cooler (radiator), 4 denotes an expansion valve (second pressure reducing device), and 5 denotes an evaporator. (Evaporator), 6 is a branch portion, 7 is an economizer (cooler), 8 is a throttle valve (first pressure reducing device), 9 is a refrigerant injection line, and each device is connected by a refrigerant pipe. A refrigeration cycle in which the refrigerant circulating in the system repeats a state change is configured.

The compressor 1 is a compression device that absorbs and compresses a gaseous CO ₂ refrigerant and discharges it to a gas cooler 2 to be described later. For example, a scroll compressor or a reciprocating compressor (crank type, swash plate type, etc.) Is adopted. Gas cooler 2
The heat exchanger cools the high-temperature and high-pressure CO ₂ refrigerant compressed by the compressor 1 with outside air or the like, and is set so that the internal pressure exceeds the critical pressure of the CO ₂ refrigerant.

The high-pressure CO ₂ refrigerant flowing out of the gas cooler 2 is divided at the branching portion 6 into one flowing directly to the economizer 7 and one flowing through the throttle valve 8 to the economizer 7. One CO ₂ refrigerant is reduced in pressure to a first predetermined pressure (intermediate pressure) P 1 by passing through the throttle valve 8, has a low temperature, and is injected into the compressor 1 through one flow path in the economizer 7. The other CO ₂ refrigerant is a refrigerated refrigerant that is supplied to the expansion valve 4 and the evaporator 5 through the other flow path in the economizer 7.

The economizer 7 is a countercurrent type heat exchanger for exchanging heat between the refrigerated refrigerant directly introduced from the gas cooler 2 and the injection refrigerant passed through the throttle valve 8, and cools the refrigerated refrigerant by the low-temperature injection refrigerant. Becomes possible. The frozen refrigerant cooled by the economizer 7 has a second predetermined pressure P lower than the first predetermined pressure P1 described above.
The pressure is reduced through an expansion valve 4 that reduces the pressure to 2, and is sent to an evaporator 5 in a gas-liquid two-phase state. Evaporator 5
Is evaporated and evaporates from the air passing through the evaporator 5, so that the air deprived of the latent heat of evaporation is cooled. The refrigerating refrigerant evaporated in this way is sucked into the compressor 1 again from the evaporator 5.

The injection refrigerant decompressed by the throttle valve 8 is cooled by the economizer 7 and then guided through the refrigerant injection line 9 to the middle of the suction compression process of the compressor 1. As a result, the refrigerated refrigerant flowing out of the evaporator 5 and the injection refrigerant injected during the compression stroke are merged in the compressor 1, and are compressed again and discharged to the gas cooler 2. Therefore, the CO ₂ refrigerant thereafter repeats the same state change and circulates through the refrigeration cycle.

The refrigerant injection line 9 is provided with an injection pressure switching means 20 for the CO ₂ refrigeration cycle having such a configuration. The injection pressure switching means 20 includes a plurality (three in the illustrated example) of the compressor 1 side of the refrigerant injection line 9.
The on-off valves 21a, 21b, 21c are provided in the branch flow paths 21, 22, 23, respectively. In this case, the compressor 1 is a scroll compressor, and each of the branch passages 21, 22, and 23 is connected to an injection port that opens at a different compression stage.

Here, the injection port provided in the scroll compressor will be briefly described with reference to FIG. In FIG. 2, reference numeral 24 in the figure denotes a fixed scroll,
25 is a fixed side wrap erected on the fixed scroll 24,
Reference numeral 26 denotes a discharge port provided on the fixed scroll, and reference numeral 27 denotes a turning-side wrap provided upright on the turning scroll. As is well known, the scroll compressor is configured such that the orbiting scroll 27 is prevented from rotating with respect to the fixed scroll 25 and revolves, and the compressed gas sucked from the suction port on the outer peripheral side is supplied to the center side. The liquid is compressed as it moves to and discharged at the highest pressure at the central discharge port 26. Fixed scroll 2 of such a scroll compressor
No. 4 has a first order from the outer peripheral side to the center discharge port 26 side.
An injection port 28, a second injection port 29, and a third injection port 30 are provided, and are respectively connected to the branch flow paths 21, 22, and 23 of the refrigerant injection line 9. In addition, each injection port 28, 29, 30 is 180
It is provided at two locations that are in a positional relationship shifted by degrees.

Therefore, the pressure in the scroll compressor is controlled by the first injection port 28 connected to the branch flow path 21 <the second injection port 29 connected to the branch flow path 22 <the second injection port 29 connected to the branch flow path 23. 3
It becomes like the injection port 30 and the on-off valve 21
By opening one appropriately selected from a, 21b, and 21c, it is possible to inject the injection refrigerant into different compression stages (that is, pressures) during the suction compression stroke in the compressor 1.

Now, assuming that the state of the gas cooler outlet side (high pressure side) refrigerant is constant, the cooling capacity of the economizer 7 is determined by the pressure (evaporation temperature) of the injection refrigerant (intermediate pressure side refrigerant) that exchanges heat with the refrigerant (the evaporation temperature). It is determined by the flow ratio of the refrigerant. Here, the flow ratio of the injection refrigerant / refrigeration refrigerant can be changed by adjusting the opening degree of the throttle valve 8. When the opening of the throttle valve 8 is increased,
That is, when the injection flow rate is increased, the intermediate pressure P1 rises, and the temperature difference with the refrigeration refrigerant decreases. However, since the mass flow rate of the CO ₂ refrigerant increases beyond the influence of the temperature difference, the cooling capacity of the economizer 7 increases, and the temperature of the refrigeration refrigerant supplied to the expansion valve 4 can be reduced. On the other hand, when the opening degree of the throttle valve 8 is reduced, that is, when the injection flow rate is reduced, the intermediate pressure P
1 decreases, and the temperature difference from the frozen refrigerant increases. However, since the mass flow rate of the CO ₂ refrigerant decreases more than the effect of the temperature difference, the cooling capacity of the economizer 7 decreases. Therefore, the cooling of the frozen refrigerant supplied to the expansion valve 4 is suppressed.

On the other hand, the pressure (evaporation temperature) of the injection refrigerant is controlled by operating the injection pressure switching means 20. That is, an optimal one is selected and opened from the on-off valves 21a, 21b, 21c according to a desired operating condition, and the pressure at which the injection refrigerant is injected, that is, the intermediate pressure is adjusted. Hereinafter, the intermediate pressure control will be described. In the configuration of this embodiment, switching between efficiency-priority operation and performance-priority operation is possible.
When efficiency is prioritized, the optimal intermediate pressure is the pressure that equally divides the pressure ratio of the system, at which time the compression work is minimized and the COP is maximized. Strictly speaking, the intermediate pressure (evaporation pressure) is determined by an injection pressure + a pipe pressure loss, and the intermediate pressure is controlled by selectively switching an injection port (a refrigerant pressure in a port portion during a compression stroke). In the illustrated embodiment, the position where the second injection port 29 is provided corresponds to this.

Next, the capacity control will be described. By changing the intermediate pressure (evaporation temperature), the temperature difference between the refrigerants (the injection refrigerant and the frozen refrigerant) in the economizer 7 can be changed. When the temperature difference is increased, the capacity of the economizer 7 increases, and the injection refrigerant has a low flow rate. Even in this case, the frozen refrigerant can be cooled down to a predetermined expansion valve inlet temperature. For this reason, the reduction rate of the amount of the refrigerated refrigerant circulating in the evaporator 5 can be reduced, and the capacity can be increased. Such control is effective under the condition that the outside air temperature is high and the cooling capacity (the enthalpy difference between the entrance and the exit in the evaporator 5) is insufficient. In addition, under the condition that the flow rate of the injection refrigerant is constant, the intermediate pressure (evaporation temperature)
When the pressure is increased, the temperature difference decreases and the capacity of the economizer 7 decreases. When the intermediate pressure is reduced, the temperature difference increases and the capacity increases. Thus, by controlling the intermediate pressure,
It is possible to control the capacity of the system according to the heat load. Such capacity control becomes more effective by appropriately combining the intermediate pressure control and the flow rate control by the throttle valve.

FIG. 3 shows the refrigerating capacity and COP characteristics (trend) by the intermediate pressure control and the injection flow rate control. According to this figure, the refrigeration capacity is high at the time of injection to the early stage (low pressure side) of the compression stroke with a low intermediate pressure, and the refrigeration capacity decreases at the time of injection to the late stage (high pressure side) of the compression stroke with a high intermediate pressure. If the flow rate of the injection refrigerant is controlled by changing the opening degree of the throttle valve 8, the characteristics of the refrigerating capacity and the COP are moved up and down as shown by the white arrows in FIG. .

Therefore, when the cooling load is large, for example, when the difference (Δt) between the set cooling temperature and the actual room temperature is large, the first injection port 28 is selected so as to increase the intermediate pressure. Employ a capacity-priority operation for obtaining a large refrigeration capacity, and select the third injection port 30 for setting the intermediate pressure to be low when the above-mentioned Δt becomes small, or select the second injection port 29 for the efficiency-priority operation. do it.
As described above, the control of the intermediate pressure (evaporation temperature on the injection refrigerant side) by the injection pressure switching means 20 and the control of the flow rate of the injection refrigerant by the throttle valve 8 can be performed together, so that the economizer capacity control and the refrigeration cycle can be performed. By the capacity control, it is possible to ensure the refrigeration capacity under the high-efficiency operation and the high outside temperature condition.

Incidentally, in the above-described embodiment, the compressor 1
Has been described as a scroll compressor, but it is of course possible to employ a reciprocating compressor such as a crank type or a swash plate type during a refrigeration cycle. In this case, the injection pressure adjusting means does not need to branch the refrigerant injection line 9 due to the compression operation of the reciprocating compressor. That is, an on-off valve may be provided in the refrigerant injection line 9, and the timing for opening and closing the on-off valve may be changed according to the compression stroke. As a result, if the on-off valve is opened at the beginning of the compression stroke, the injection pressure becomes low, and if the on-off valve is opened at the later stage of the compression stroke, the injection pressure becomes high, so that the optimal injection pressure according to the desired operating condition is obtained. And the same operation and effect as those of the scroll compressor described above can be obtained.

<Second Embodiment> A second embodiment shown in FIG. 4 shows a CO ₂ refrigeration cycle using an economizer 7 and an intercooler 10 in combination. FIG. 4 (a)
In the configuration diagram shown in FIG. 1, reference numeral 10 denotes an intercooler, SV1 denotes a first opening / closing valve, SV2 denotes a second opening / closing valve, and SV3
Is a third on-off valve, SV4 fourth on-off valve, 31 is a first bypass line, and 32 is a second bypass line. The other components are the same as those in the first embodiment described above, and a detailed description thereof will be omitted.

In this CO ₂ refrigeration cycle, the economizer 7 and the intercooler 10 are arranged in series, and the single use of the economizer 7, the single use of the intercooler 10, and the combined use of the economizer 7 and the intercooler 10 are performed according to the operating conditions. To make an appropriate selection. The first on-off valve SV1 is arranged between the gas cooler 2 and the branch portion 6, and the second on-off valve SV2 is arranged between the economizer 7 and the intercooler 10.

The first bypass line 31 is connected to the gas cooler 3
1 and the first on-off valve SV1, the second on-off valve S
The third on-off valve SV3 is connected between the V2 and the intercooler 10, and is disposed in the middle of the first bypass line 31. That is, the first bypass line 31 forms a refrigerant flow path that bypasses the branch part 6 and the economizer 7. The second bypass line 32 branches from between the economizer 7 and the second on-off valve SV2 and is connected between the intercooler 10 and the evaporator 5.
A fourth on-off valve SV4 is disposed in the middle of the bypass line 32. That is, the second bypass line 32 forms a refrigerant flow path that bypasses the intercooler 10.

With such a configuration, during operation using the economizer 7 and the intercooler 10 together, FIG.
As shown in the valve opening / closing matrix of (b), the first opening / closing valve SV1 and the second opening / closing valve SV2 are opened, and the third opening / closing valve SV3 is opened.
By closing the fourth on-off valve SV4, the first bypass line 31 and the second bypass line 32 are closed, and the CO ₂ refrigerant that has left the compressor 1 is supplied to the gas cooler 2, the economizer 7, the intercooler 10, the expansion valve 4, And evaporator 5
To form a CO ₂ refrigeration cycle flowing through.

When the economizer 7 operates alone,
As shown in the valve opening / closing matrix in FIG. 4B, the first opening / closing valve SV1 and the fourth opening / closing valve SV4 are opened, and the second opening / closing valve S4 is opened.
By closing V2 and the third on-off valve SV3, the second bypass line 32 is brought into a communicating state. As a result, the first bypass line 32 is closed, and the CO ₂ refrigerant that has exited the compressor 1 passes through the gas cooler 2, the economizer 7, the second bypass line 32, the expansion valve 4, and the evaporator 5, and passes through the intercooler 7. A CO ₂ refrigeration cycle that flows by bypass can be formed.

Further, during operation of the intercooler 10 alone, as shown in the valve opening / closing matrix of FIG.
Only the third on-off valve SV3 is opened, and the first on-off valve SV1,
By closing the on-off valve SV2 and the fourth on-off valve SV4, the first bypass line 31 is brought into a communicating state. As a result, the second bypass line 32 is closed, and the CO
_{The 2} refrigerant passes through the gas cooler 2, the first bypass line 31, the intercooler 10, the expansion valve 4 and the evaporator 5 and bypasses the economizer 7.
_Two refrigeration cycles can be formed.

Therefore, the operation using the economizer 7 alone can lower the suction temperature of the compressor 1 as compared with the operation using the intercooler 7 alone, which is advantageous in terms of compression efficiency, and The discharge temperature of the compressor 1 can be suppressed. In particular, since the discharge temperature of the CO ₂ refrigerant is high due to its physical properties, deterioration of the refrigerating machine oil (lubricating oil) and the sealing surface becomes a problem under operating conditions with a large pressure ratio. Therefore, an economizer is required to improve the durability. 7 is advantageous. On the other hand, under operating conditions in which the pressure ratio is small and the discharge temperature does not need to be suppressed, the intercooler 1 which can lower the inlet temperature of the expansion valve 4 and can increase the cooling capacity.
Adopt zero operation. If further cooling capacity is required, it can be dealt with by performing an operation using both the economizer 7 and the intercooler 10.

As described above, the economizer alone operation for suppressing the discharge temperature, the intercooler alone operation for increasing the capacity, and the economizer / intercooler combined operation suitable for further increasing the capacity are selectively used to improve the durability. The operation time of the economizer, which is disadvantageous in the above, can be shortened, and both the expansion of the cooling capacity and the improvement of the durability and reliability can be achieved. The operation switching operation described above may be performed, for example, by detecting the temperature of the refrigerant discharged from the compressor 1.

<Third Embodiment> A third embodiment shown in FIG. 5 is a combination of the first embodiment and the second embodiment described above, and each component is denoted by the same reference numeral. And a detailed description thereof will be omitted. With such a configuration, the injection pressure of the injection refrigerant can be controlled by the injection pressure switching means 20 during the operation using the economizer 7 in the second embodiment, that is, during the economizer alone operation and the economizer / intercooler combined operation. Becomes For this reason, in addition to the control of the flow rate of the injection refrigerant by the throttle valve 8, high-efficiency operation by the control of the intermediate pressure (injection-side evaporation temperature) and the cooling capacity at the time of high outside air temperature can be secured.

<Fourth Embodiment> The CO ₂ refrigeration cycle of a fourth embodiment shown in FIG. 6 uses two compressors which can be operated independently. The first embodiment shown in FIG. Therefore, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted. That is, the low-stage compressor 1L and the high-stage compressor 1H are connected in series, and include a gas cooler 2, an ecomanizer 7, a high-pressure control valve 3, an expansion valve 4, an evaporator 5, and a throttle valve 8. In this CO ₂ refrigeration cycle, the optimum high pressure with respect to the gas cooler outlet temperature is controlled at the economizer outlet.

In FIG. 6, the refrigerant discharged from the low-stage compressor 1L is further pressurized by the high-stage compressor 1H, enters the gas cooler 2, and radiates heat of the refrigerant. Gas cooler 2
Of the outlet refrigerant flowing out of the pump (injection refrigerant)
Is diverted at the branch portion 6 and passes through the throttle valve 8, so that the pressure is reduced and cooled to a two-phase region of gas and liquid. Then, by performing heat exchange between the injection refrigerant and the remaining refrigerant (refrigerant refrigerant) flowing from the branch portion 6 to the economizer 7 side by the economizer 7, the temperature of the refrigerant at the inlet of the expansion valve 4 is reduced, and a cooling effect is obtained. . The injection refrigerant that has flowed out of the economizer 7 flows into the discharge section of the low-stage compressor 1L, and again takes the latent heat of evaporation from the refrigerant to lower the suction temperature of the high-stage compressor 1H. That is, the discharge temperature of the high-stage compressor 1H can be suppressed by this operation. On the other hand, the refrigerated refrigerant radiated and cooled by the economizer 7 passes through the high-pressure control valve 3 and the expansion valve 4, absorbs heat by the evaporator 5, and is sucked into the low-stage compressor 1L.

In the CO ₂ refrigeration cycle of FIG. 10 described in the related art, the inlet temperature of the expansion valve 4 can be reduced only to the outside air temperature + α ° C., and the cooling capacity (enthalpy difference) depends on the outside air temperature. . In contrast, the CO shown in FIG.
_{In the two-} refrigeration cycle, the economizer 7 can lower the refrigerant temperature at the inlet of the expansion valve 4 to near the refrigerant temperature at the outlet of the throttle valve 8, so that a sufficient cooling capacity (enthalpy difference) can be ensured.

As a wide range of operation performance, for example, under conditions where the outside air temperature is high and the cooling capacity (enthalpy difference) is small,
By increasing the discharge pressure by increasing the speed of only the high-stage compressor 1H and increasing the amount of work in the economizer 7, the expansion valve 4
Temperature can be lowered to obtain a cooling effect. Here, it is assumed that the low-stage compressor 1L and the high-stage compressor 1H can independently control the rotation speed, and the rotation speed control means may employ inverter control or pole number conversion. Further, as another method, the intermediate pressure (evaporation temperature of the injection refrigerant) as in the above-described first embodiment and the like.
Lowering the cooling capacity (enthalpy difference).

As described above, in this CO ₂ refrigeration cycle, the suction temperature of the high-stage compressor 1H is also reduced by the latent heat of vaporization of the injection refrigerant, so that the discharge temperature of the high-stage compressor 1H can be suppressed. As described above, in the present CO ₂ refrigeration cycle, the operation of the two compressors 1L and 1H is independently controlled in accordance with the operating conditions, and the high-pressure pressure, the intermediate pressure, and the refrigeration refrigerant flowing through the economizer 7 are controlled. The efficiency priority operation and the capacity priority operation can be selectively controlled according to the situation.

The parameters for realizing high-efficiency operation are as follows. (1) Regarding the control of the high pressure, control is performed such that the optimum high pressure (MPa) with respect to the gas cooler outlet temperature (° C.) becomes a value shown in FIG. (In this CO ₂ refrigeration cycle,
The optimum high pressure is the outlet pressure of the economizer 7. (2) As for the intermediate pressure, as shown in [Equation 1], the pressure ratio between the low-stage compressor 1L and the high-stage compressor 1H is made equal pressure ratio.

(Equation 1) (3) The injection refrigerant flow rate is a flow rate at which latent heat of evaporation required to lower the inlet temperature of the expansion valve 4 to a limit is obtained. (To suppress the discharge temperature of the high-stage compressor 1H,
The flow rate of the injection refrigerant is increased from the above flow rate. ) Expansion valve inlet temperature = Evaporation temperature of economizer (two-phase side) +
α ° Here, α is determined by the capacity of the economizer 7.

<Fifth Embodiment> In this embodiment, in the CO ₂ refrigeration cycle, which is a supercritical cycle, the optimum amount of refrigerant is reliably determined based on the flow state of the liquid refrigerant in the same manner as the conventional CFC-based refrigerant. For example, a supercooling control valve 11, an intermediate pressure receiver 12, and a sight glass 13 are additionally provided in the fourth embodiment shown in FIG. In the CO ₂ refrigeration cycle shown in FIG. 8, the outlet of the supercooling control valve 11 is at a supercritical pressure, and when adiabatically expanded from this state, the refrigerant changes from supercritical (gas phase) → liquid phase → two phases. In the Mollier diagram, a region surrounded by the critical pressure and the saturated liquid line is a liquid phase.

In this CO ₂ refrigeration cycle, during the adiabatic expansion process, the supercooling control valve 11 reduces the pressure (liquid phase) between the critical pressure and the saturated liquid pressure, and the intermediate pressure receiver 12 holds the excess refrigerant. At the same time, the optimum amount of refrigerant is determined from the flow state of the refrigerant in the sight glass 13 provided as the visual recognition unit. In addition, the above-described configuration of the present invention may be applied to a single-stage compressor without the economizer 7 shown in FIG. 10, for example, except for a multi-stage compression in which a plurality of compressors are arranged in series or a supercritical vapor compression refrigeration cycle with the economizer 7 The present invention can be applied to all supercritical vapor compression refrigeration cycles that form a supercritical cycle, such as a refrigeration cycle of a compression configuration. In such a case, the refrigerant flowing out of the gas cooler 2 is depressurized to a liquid phase region. The supercooling control valve 11 and the intermediate pressure receiver 12 as means may be provided on the downstream side of the high pressure control valve 3 or on the downstream side of the gas cooler 2 if the high pressure control valve 3 is not provided.

The sight glass 13 serving as the visual recognition part is provided so as to be located below the intermediate pressure receiver 12, or is provided independently at the outlet of the intermediate pressure receiver 12. Thereby, the flow state of the liquid refrigerant can be easily determined. As a means for reducing the pressure of the refrigerant flowing out of the gas cooler 2 to the liquid phase region, for example, a pressure control valve or the like can be employed in addition to the above-described supercooling control valve 11.

<Sixth Embodiment> CO _{2 of} this embodiment
In the refrigeration cycle, a gas return circuit 14 for extracting the gas-phase refrigerant separated by the intermediate pressure receiver 12 to the suction section of the high-stage compressor 1H is different from the refrigeration cycle of the fifth embodiment shown in FIG. The gas return circuit 14 is provided with a gas return amount adjusting valve 15. In the fifth embodiment described above, the inside of the intermediate pressure receiver 13 is controlled to the liquid phase region in order to check the flow state of the liquid refrigerant. However, in the configuration of the present embodiment, the refrigerant amount can be checked and It becomes a CO ₂ refrigeration cycle that can operate efficiently.

In the CO ₂ refrigeration cycle according to the sixth embodiment shown in FIG. 9, the pressure in the intermediate pressure receiver 12 is increased by the supercooling control valve 11 to a level higher than the suction pressure of the high-stage compressor 1H and Control below pressure. Under such conditions, the inside of the intermediate pressure receiver 12 is in a gas-liquid two-phase state, and a liquid refrigerant and a gas-phase refrigerant are mixed. However, only the liquid refrigerant component evaporates in the evaporator 5 and can obtain the cooling effect, and the gas-phase refrigerant does not perform cooling work. Therefore, even if the gas-phase refrigerant is bled from the intermediate pressure receiver 12 to the high-stage compressor 1H from the gas return circuit 14, the circulation amount of the liquid refrigerant does not substantially change, so that the cooling capacity of the evaporator 5 does not change. Become. The function of the gas return amount adjusting valve 15 is to suck and extract only the gas components separated in the intermediate pressure receiver into the high-stage compressor.

As described above, the operation of extracting the gas-phase refrigerant in the intermediate pressure receiver 12 reduces the amount of refrigerant circulated in the low-stage compressor 1L, so that the power consumption of the low-stage compressor 1L decreases. In addition, since the power of the compressor as a whole is also reduced, the COP is improved. As for the amount of the refrigerant, the flow of the liquid refrigerant component separated by the intermediate pressure receiver 12 can be confirmed by viewing from the sight glass 13.

In the above embodiments, the refrigerant is described as CO ₂ , but the present invention is not limited to this.
Needless to say, the present invention can be applied to a supercritical vapor compression refrigeration cycle using another refrigerant. Any configuration may be employed without departing from the gist of the present invention. Needless to say, the configurations of the above-described embodiments may be appropriately combined.

[0065]

According to the supercritical vapor compression refrigeration cycle of the present invention, the following effects can be obtained. According to the supercritical vapor compression refrigeration cycle according to the first aspect, since both the flow rate control of the injection refrigerant and the injection pressure can be controlled, high performance can be achieved by controlling the economizer capacity and the refrigeration cycle. Efficient operation and cooling capacity under high outside air temperature conditions can be secured.

According to the supercritical vapor compression refrigeration cycle of the present invention, a refrigeration cycle using an economizer to suppress the discharge temperature of the compressor and a refrigeration using an intercooler to expand the cooling capacity. It is possible to appropriately select a cycle and a refrigeration cycle using an economizer and an intercooler in order to further increase the cooling capacity according to the operating conditions. Therefore, it is possible to improve the durability and reliability by suppressing the deterioration of the refrigerating machine oil and the seal surface due to the rise in the discharge temperature. Large cooling capacity can be obtained.

According to the supercritical vapor compression refrigeration cycle of the third aspect, the refrigeration cycle uses an economizer to suppress the discharge temperature of the compressor, and the refrigeration uses an intercooler to expand the cooling capacity. Cycle and a refrigeration cycle that uses an economizer and an intercooler in order to further increase the cooling capacity can be appropriately selected according to the operating conditions.Moreover, during operation using the economizer, the injection refrigerant Flow rate control and injection pressure control can be used together. For this reason, durability and reliability are improved, and a large cooling capacity can be obtained in a situation where a cooling capacity is required. In particular, when an economizer is used,
Higher efficiency operation and higher cooling capacity in high outside air temperature conditions can be ensured.

According to the supercritical vapor compression refrigeration cycle of the present invention, since the refrigeration cycle is a two-stage compression and one-stage expansion refrigeration cycle, each compressor operates independently to ensure refrigerating capacity over a wide range and achieve high efficiency. Can be achieved.

[0069] According to the supercritical vapor compression refrigeration cycle of the tenth aspect, the refrigerant is brought into a liquid phase downstream of the radiator,
Since the flow state of the refrigerant can be checked from the visual sight glass provided in the intermediate pressure receiver, the optimum refrigerant amount can be visually determined even in the supercritical vapor compression refrigeration cycle.

In the supercritical vapor compression refrigeration cycle according to the twelfth aspect, the inside of the intermediate pressure receiver is in a gas-liquid two-phase state, and the gas-phase refrigerant that does not perform cooling work in the evaporator is supplied to the suction side of the high-pressure compressor. The driving force consumed in the low-pressure stage compressor can be reduced, and the COP can be improved accordingly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment of a supercritical vapor compression refrigeration cycle of the present invention.

FIG. 2 is an explanatory diagram showing an example of an arrangement of an injection port in a scroll compressor.

FIG. 3 is a diagram showing a relationship between an intermediate pressure and a refrigerating capacity and a relationship between an intermediate pressure and a COP.

FIGS. 4A and 4B are diagrams showing a second embodiment of the supercritical vapor compression refrigeration cycle of the present invention, wherein FIG. 4A is a configuration diagram of a refrigeration cycle, and FIG. 4B is a diagram showing a valve opening / closing matrix.

FIG. 5 is a configuration diagram illustrating a third embodiment of the supercritical vapor compression refrigeration cycle of the present invention.

FIG. 6 is a configuration diagram showing a fourth embodiment of the supercritical vapor compression refrigeration cycle of the present invention.

7A and 7B are diagrams showing high-pressure control characteristics, in which FIG. 7A is a diagram showing the relationship between high-pressure and COP, and FIG. 7B is a diagram showing the relationship between gas cooler outlet temperature and optimum high-pressure.

FIG. 8 is a configuration diagram showing a fifth embodiment according to the supercritical vapor compression refrigeration cycle of the present invention.

FIG. 9 is a configuration diagram showing a sixth embodiment of the supercritical vapor compression refrigeration cycle of the present invention.

FIG. 10 is a configuration diagram showing a conventional vapor compression refrigeration cycle.

11 is a Mollier chart of the vapor compression refrigeration cycle shown in FIG.

FIG. 12 is a configuration diagram showing a conventional economizer cycle.

FIG. 13 is a diagram showing a configuration example of a conventional vapor compression refrigeration cycle using an intercooler.

[Explanation of symbols]

 Reference Signs List 1 compressor (compressor) 1L low-stage compressor (compressor) 1H high-stage compressor (compressor) 2 gas cooler (radiator) 4 expansion valve (second decompressor) 5 evaporator (evaporator) 7 economizer 8 throttle Valve (first pressure reducing device) 9 Refrigerant injection line 10 Intercooler 11 Subcooling control valve (means for reducing pressure) 12 Intermediate pressure receiver 13 Sight glass (visual means) 14 Gas return circuit (gas release circuit) 15 Gas return amount adjusting valve Reference Signs List 20 injection pressure switching means 21, 22, 23 Branch flow path 31 First bypass line 32 Second bypass line

Claims (13)

[Claims] 1. A radiator that cools a compressed refrigerant and whose internal pressure exceeds a critical pressure of the refrigerant; a branch portion that branches the refrigerant flowing out of the radiator; A first decompression device for decompressing the refrigerant to a first predetermined pressure, an economizer for exchanging heat between the refrigerant decompressed by the first decompression device and the other refrigerant, and cooling the other refrigerant, and the economizer. A second decompression device that decompresses the refrigerant on the other side cooled to a second predetermined pressure lower than the first predetermined pressure; an evaporator that evaporates the refrigerant depressurized by the second decompression device; A compression device that absorbs and compresses the refrigerant flowing out of the evaporator and discharges the refrigerant toward the radiator, and guides the refrigerant decompressed by the first decompression device to the middle of a suction compression process of the compression device. Refrigerant injection line A supercritical vapor compression refrigeration cycle equipped with supercritical vapor compression refrigeration cycle, characterized in that a injection pressure switching means to said coolant injection line. 2. A radiator that cools the compressed refrigerant and whose internal pressure exceeds the critical pressure of the refrigerant; a branch portion that branches the refrigerant flowing out of the radiator; A first decompression device for decompressing the refrigerant to a first predetermined pressure, an economizer for exchanging heat between the refrigerant decompressed by the first decompression device and the other refrigerant, and cooling the other refrigerant, and the economizer. A second decompression device that decompresses the refrigerant on the other side cooled to a second predetermined pressure lower than the first predetermined pressure; an evaporator that evaporates the refrigerant depressurized by the second decompression device; An intercooler located between the economizer and the evaporator, for cooling the refrigerant on the other side with the refrigerant flowing out of the evaporator, and absorbing and compressing the refrigerant flowing out of the evaporator through the intercooler, Radiator A supercritical vapor compression refrigeration cycle, comprising: a refrigerant injection line for guiding the refrigerant decompressed by the first decompression device to the middle of a suction compression process of the compression device. A first on-off valve installed between the radiator and the branch portion; a second on-off valve installed between the economizer and the intercooler; and between the radiator and the first on-off valve. A first bypass line that is connected between the second on-off valve and the intercooler and has a third on-off valve in the middle thereof, and that branches off from between the economizer and the second on-off valve. A supercritical vapor compression refrigeration cycle, comprising a second bypass line connected between an intercooler and the second pressure reducing device and provided with a fourth on-off valve on the way. 3. A radiator that cools the compressed refrigerant so that the internal pressure exceeds the critical pressure of the refrigerant; a branch that branches the refrigerant flowing out of the radiator; A first decompression device for decompressing the refrigerant to a first predetermined pressure, an economizer for exchanging heat between the refrigerant decompressed by the first decompression device and the other refrigerant, and cooling the other refrigerant, and the economizer. A second decompression device that decompresses the refrigerant on the other side cooled to a second predetermined pressure lower than the first predetermined pressure; an evaporator that evaporates the refrigerant depressurized by the second decompression device; An intercooler located between the economizer and the evaporator, for cooling the refrigerant on the other side with the refrigerant flowing out of the evaporator, and absorbing and compressing the refrigerant flowing out of the evaporator through the intercooler, Radiator A supercritical vapor compression refrigeration cycle, comprising: a refrigerant injection line for guiding the refrigerant decompressed by the first decompression device to the middle of a suction compression process of the compression device. Providing an injection pressure switching means in the refrigerant injection line, a first on-off valve installed between the radiator and the branch portion, and a second on-off valve installed between the economizer and the intercooler. A first bypass line branched from between the radiator and the first on-off valve and connected between the second on-off valve and the intercooler and including a third on-off valve on the way; A second bypass line branched from between the second on-off valve and connected between the intercooler and the second pressure reducing device and including a fourth on-off valve on the way. And a supercritical vapor compression refrigeration cycle. 4. The compressor according to claim 1, wherein the compression device is a scroll compressor having a plurality of injection ports, and the injection pressure switching means branches the injection line into a plurality of parts, and provides an on-off valve for each of the plurality of injection lines. 2. The method according to claim 1, wherein the injection ports are connected to different injection ports.
Or the supercritical vapor compression refrigeration cycle according to 3. 5. The ultra-compact compressor according to claim 1, wherein said compression device is a reciprocating type, and said injection pressure switching means adjusts an opening / closing operation timing of an on-off valve provided on said injection line. Critical vapor compression refrigeration cycle. 6. The switching of the first on-off valve, the second on-off valve, the third on-off valve, and the fourth on-off valve by detecting the temperature of the refrigerant discharged from the compression device. The supercritical vapor compression refrigeration cycle according to claim 2. 7. A radiator that cools the compressed refrigerant and has an internal pressure exceeding the critical pressure of the refrigerant, a branch portion for branching the refrigerant flowing out of the radiator, and one of the branched portions at the branch portion. A first decompression device for decompressing the refrigerant to a first predetermined pressure, an economizer for exchanging heat between the refrigerant depressurized by the first decompression device and the other refrigerant to cool the other refrigerant, and the economizer. A second decompression device that decompresses the refrigerant on the other side cooled to a second predetermined pressure lower than the first predetermined pressure; an evaporator that evaporates the refrigerant depressurized by the second decompression device; A compression device that absorbs and compresses the refrigerant flowing out of the evaporator and discharges the refrigerant toward the radiator, and guides the refrigerant decompressed by the first decompression device to the middle of a suction compression process of the compression device. Refrigerant injection line A supercritical vapor compression refrigeration cycle, comprising: a plurality of compressors in which the compressor is arranged in series, wherein the refrigerant injection line is connected between the plurality of compressors. Compression refrigeration cycle. 8. The supercritical vapor compression refrigeration cycle according to claim 7, wherein high pressure control is performed at an outlet of the economizer. 9. The supercritical vapor compression refrigeration cycle according to claim 7, wherein the rotation speed of each of the plurality of compressors is independently controlled. 10. A radiator that cools the compressed refrigerant so that the internal pressure exceeds the critical pressure of the refrigerant; a decompression device that depressurizes the refrigerant flowing out of the radiator to a predetermined pressure; A supercritical vapor compression refrigeration cycle comprising: an evaporator that evaporates the refrigerant that has been evaporated; and a compression device that absorbs and compresses the refrigerant flowing out of the evaporator and discharges the refrigerant toward the radiator. A refrigerant amount management means comprising: means for reducing the pressure of the refrigerant flowing out to a liquid phase region; an intermediate pressure receiver for holding surplus refrigerant; and a visual recognition unit for judging the flow state of the liquid refrigerant. Supercritical vapor compression refrigeration cycle. 11. The supercritical vapor compression refrigeration cycle according to claim 10, wherein the visual recognition unit is provided at a lower portion or an outlet of the intermediate pressure receiver. 12. A radiator that cools the compressed refrigerant so that the internal pressure exceeds the critical pressure of the refrigerant, a branch portion that branches the refrigerant flowing out of the radiator, and one of the branched portions. A first decompression device for decompressing the refrigerant to a first predetermined pressure, an economizer for exchanging heat between the refrigerant depressurized by the first decompression device and the other refrigerant to cool the other refrigerant, and the economizer. A second decompression device that decompresses the refrigerant on the other side cooled to a second predetermined pressure lower than the first predetermined pressure; an evaporator that evaporates the refrigerant depressurized by the second decompression device; A compression device that absorbs and compresses the refrigerant flowing out of the evaporator and discharges the refrigerant toward the radiator, and guides the refrigerant decompressed by the first decompression device to the middle of a suction compression process of the compression device. Refrigerant injection line A supercritical vapor compression refrigeration cycle comprising: wherein the compression device comprises a low-stage compressor and a high-stage compressor arranged in series, and the refrigerant injection line is connected between the low-stage compressor and the high-stage compressor. And a means for reducing the pressure of the refrigerant flowing out of the economizer to a two-phase region, an intermediate pressure receiver for holding the surplus refrigerant, and a visual recognition unit for judging the flow state of the liquid refrigerant. Means for connecting the upper part of the intermediate pressure receiver to the suction side of the high-pressure stage compressor, and a gas-phase refrigerant from the intermediate pressure receiver in a gas-liquid two-phase region state to the high-pressure stage. A supercritical vapor compression refrigeration cycle characterized in that it is configured to extract air to a suction side of a compressor. 13. The supercritical vapor compression refrigeration cycle according to claim 12, wherein the flow state of the liquid refrigerant component separated in the intermediate pressure receiver is checked by a visual recognition unit to determine the amount of the refrigerant.