WO2018025900A1

WO2018025900A1 - Refrigeration device and control method therefor

Info

Publication number: WO2018025900A1
Application number: PCT/JP2017/028003
Authority: WO
Inventors: 村上　健一; 篤塩谷
Original assignee: 三菱重工サーマルシステムズ株式会社
Priority date: 2016-08-04
Filing date: 2017-08-02
Publication date: 2018-02-08
Also published as: EP3462108A4; EP3462108A1; JP6692715B2; JP2018021721A

Abstract

A refrigeration device is equipped with: an extraction pipe (19) that extracts a portion of a non-azeotropic refrigerant mixture from between a condenser (5) and an expansion valve (7); an extraction pipe on-off valve (20); a gas-liquid separator (17) that is connected to the extraction pipe (19), and that accumulates the non-azeotropic refrigerant mixture and separates the mixture into a gas and a liquid; a gas return pipe (21) connecting the gas-phase portion inside the gas-liquid separator (17) and a point between the expansion valve (7) and an evaporator (9); a gas return pipe on-off valve (22); a liquid return pipe (23) connecting the liquid-phase portion inside the gas-liquid separator (17) and a point between the expansion valve (7) and the evaporator (9); a liquid return pipe on-off valve (24); and a control unit that controls the extraction pipe on-off valve (20), the gas return pipe on-off valve (22), and the liquid return pipe on-off valve (24).

Description

Refrigerating apparatus and control method thereof

The present invention relates to a refrigeration apparatus using a non-azeotropic mixture refrigerant and a control method thereof.

As a refrigerant used for an air conditioner, HFC refrigerants, such as R410A, are used. However, the HFC refrigerant represented by R410A has a high GWP (global warming potential). Therefore, among HFC refrigerants, R32 having a GWP lower than that of R410A, and HFO refrigerants 1234yf and R1234ze (E) are listed as candidates for the next refrigerant for R410A. However, due to the physical properties of fluorocarbon refrigerant and natural refrigerant, there are advantages and disadvantages in the refrigerants to be the next candidate. For example, R32 has lower GWP and can obtain equal or higher performance than R410A, but has the disadvantage of high discharge temperature and inferior reliability in a low temperature range compared to R410A. Although R1234yf and R1234ze (E) have the advantage of having a low GWP with a GWP of 10 or less, they are only about 50% in volume capacity due to their low density compared to R410A, and to ensure equivalent performance There is a disadvantage that the size of the device is increased.

In order to compensate for such advantages and disadvantages of the refrigerant, use of a mixed refrigerant in which two or more types of refrigerants are mixed has been considered. Patent Document 1 below discloses changing the ratio of the mixed refrigerant in the refrigeration cycle by dissolving the mixed refrigerant in the refrigerator oil and utilizing the difference in the solubility of the refrigerant.

JP-A-7-98161

Among the mixed refrigerants, a non-azeotropic mixed refrigerant in which refrigerants having different boiling points are mixed causes temperature slippage as shown in FIG. That is, since the boiling points and condensation points of the mixed refrigerants are different, the isotherm in the wet vapor (between the saturated liquid line and the saturated vapor line) does not become constant in pressure (p) like a single refrigerant, p It is an isothermal line falling to the right on the -h diagram. That is, temperature slippage occurs in the non-azeotropic mixed refrigerant.

Further, depending on the proportions of the refrigerants in the non-azeotropic mixture refrigerant, for example, as shown in FIG. 12, the temperature difference of the temperature slip differs. 12, the horizontal axis represents the mixing ratio [wt%] of R32 (low boiling point refrigerant) to R1234ze (E) (high boiling point refrigerant), and the vertical axis represents the high pressure side (FIG. 12A: saturation temperature 40 ° C.) The temperature difference [° C.] of the temperature slip on the low pressure side (FIG. 12B: saturation temperature 10 ° C.) is shown. As can be seen from the figure, the temperature slip is maximum at a mixing ratio of R32 to R1234ze (E) of about 20 wt%. In this case, since the saturation temperature is 10 ° C. on the low pressure side, there is a possibility that the low temperature side, that is, the evaporator temperature becomes 0 ° C. or less, and frost may be formed on the evaporator. When the heating operation is performed, when the evaporator is frosted, the heat exchange performance is reduced and the heat absorption amount is reduced, so that the decrease in the heating performance becomes remarkable.

FIG. 13 shows COPs (coefficients of performance) at the time of cooling operation and at the time of heating operation when the mixing ratio of R410A and R1234ze (E) is changed. In the figure, the horizontal axis (lower axis) is the mixing ratio [wt%] of R32 to R1234ze (E), the horizontal axis (upper axis) is GWP in each mixing ratio, and the vertical axis is R410A It is considered as COP in the same ability ratio to. As can be seen from the figure, when the R32 mixture ratio decreases, the ratio of R1234ze (E) increases, so the GWP decreases, but the COPs during the cooling operation and the heating operation decrease, especially the COP decreases during the cooling operation .

Therefore, it is desirable to make the mixing ratio of the non-azeotropic mixture refrigerant performing the refrigeration cycle variable during operation. Although the ratio of the mixed refrigerant in the refrigeration cycle can be changed in the above-mentioned Patent Document 1, it is necessary to control the temperature and the oil storage amount of the refrigerator oil since the solubility of the refrigerant in the refrigerator oil is used. It may be complicated.

The present invention has been made in view of such circumstances, and provides a refrigeration apparatus that can change the mixing ratio of non-azeotropic refrigerants that perform refrigeration cycles with a simple configuration during operation, and a control method thereof. With the goal.
Another object of the present invention is to provide a refrigeration system and a control method thereof that can prevent frost formation on the evaporator temperature due to temperature slip of the non-azeotropic mixture refrigerant.
Another object of the present invention is to provide a refrigeration system using a non-azeotropic mixed refrigerant that can suppress performance deterioration during cooling operation as much as possible, and a control method thereof.

In order to solve the above-mentioned subject, the freezing device and its control method of the present invention adopt the following means.
That is, a refrigeration apparatus according to one aspect of the present invention includes a compressor for compressing a non-azeotropic refrigerant mixture in which low boiling point refrigerants having different boiling points and high boiling point refrigerant are mixed, and a non-azeotropic refrigerant introduced from the compressor A condenser for condensing mixed refrigerant, an expansion valve for expanding non-azeotropic mixed refrigerant led from the condenser, an evaporator for evaporating the non-azeotropic mixed refrigerant led from the expansion valve, and the condenser A takeout pipe for taking out part of the non-azeotropic mixture refrigerant from between the expansion valve and the expansion valve, an open / close valve for takeout piping provided in the takeout piping, and the takeout pipe connected to store the non-azeotropic mixture refrigerant Gas-liquid separator, a gas return pipe connecting between the expansion valve and the evaporator, and a gas phase part in the gas-liquid separator, and the gas return pipe A gas return pipe on-off valve, between the expansion valve and the evaporator, and in the gas-liquid separator A liquid return pipe connecting the phase portion, a liquid return pipe on-off valve provided on the liquid return pipe, the outlet pipe on-off valve, the gas return pipe on-off valve, and the liquid return pipe on-off valve And a control unit to control.

By opening the on-off valve for the discharge pipe according to a command from the control unit, a part of the non-azeotropic mixed refrigerant is taken out from between the condenser and the expansion valve via the discharge pipe, and temporarily used as a gas-liquid separator. Retain. In the gas-liquid separator, the gas-liquid is separated according to the temperature and pressure in the gas-liquid separator to form a liquid phase portion and a gas phase portion.
When the on / off valve for gas return piping is opened according to a command from the control unit, the gas phase portion of the gas / liquid separator is communicated between the expansion valve and the evaporator via the gas return piping, and the pressure in the gas phase portion is low. Thus, the low boiling point refrigerant is preferentially led to the evaporator. Thereby, the ratio of the low boiling point refrigerant in the non-azeotropic refrigerant mixture in which the refrigeration cycle is performed can be increased.
When the liquid return piping on-off valve is opened according to a command from the control unit, the liquid phase portion of the gas-liquid separator is communicated between the expansion valve and the evaporator through the liquid return piping, and the liquid refrigerant in the liquid phase Are led to the evaporator. In the gas-liquid separator, low-boiling point refrigerant evaporates and is separated from the liquid phase portion, so high-boiling point refrigerant is present in the liquid refrigerant at a higher ratio than when non-azeotropic mixed refrigerant is taken out from the outlet piping. doing. Thereby, the ratio of the high boiling point refrigerant in the non-azeotropic refrigerant mixture in which the refrigeration cycle is performed can be increased.
As described above, the refrigerant that has been separated by the gas-liquid separator can be returned from the gas phase portion or the liquid phase portion into the refrigeration cycle only by controlling the on-off valves of the pipes connected to the gas-liquid separator. Therefore, the mixing ratio of the low boiling point refrigerant and the high boiling point refrigerant can be arbitrarily changed by a simple configuration.
Examples of the low boiling point refrigerant include R32, and examples of the high boiling point refrigerant include R1234yf and R1234ze (E).

Furthermore, in the refrigeration apparatus according to one aspect of the present invention, the control unit performs the on-off valve for the extraction pipe when the outside air temperature is less than a predetermined value or the temperature of the evaporator is less than a predetermined value during heating operation. Is opened, and the on-off valve for the gas return pipe is opened to perform a separation operation in which the gas refrigerant separated by the gas-liquid separator is returned from the gas return pipe to the evaporator side.

During heating operation, the temperature of the evaporator is generally low because the outside air temperature is low. When the temperature of the evaporator falls below a predetermined value, for example, a problem such as frost formation on the evaporator occurs. Therefore, when the outside air temperature is less than the predetermined value or the temperature of the evaporator is less than the predetermined value, the gas refrigerant separated by the gas-liquid separator (mainly the low boiling point) is opened by opening the on-off valve for gas return piping. The refrigerant is returned to the evaporator side through the gas return pipe to increase the proportion of the low boiling point refrigerant in the refrigeration cycle. At this time, by opening the on-off valve for the extraction pipe, the non-azeotropic mixed refrigerant is introduced from the refrigeration cycle to the gas-liquid separator from the refrigeration cycle, and gas-liquid separation is performed in the gas-liquid separator to achieve low boiling point. Returning the refrigerant back to the refrigeration cycle further promotes an increase in the proportion of low boiling point refrigerant in the refrigeration cycle.
By performing such separation operation, separation operation is performed to separate the high boiling point refrigerant from the non-azeotropic mixed refrigerant that performs the refrigeration cycle to increase the proportion of the low boiling point refrigerant, thereby reducing the temperature slip, and the evaporator It is possible to raise the saturation temperature at the point where it is possible, for example, to suppress
The predetermined value of the outside air temperature or the predetermined value of the temperature of the evaporator is, for example, a temperature at which the temperature of the evaporator may decrease to cause frost formation.

Furthermore, in the refrigeration apparatus according to one aspect of the present invention, the control unit causes the degree of superheat of the non-azeotropic mixture refrigerant sucked by the compressor to be less than a predetermined value after a predetermined period has elapsed since the start of the separation operation. After that, the on-off valve for the extraction pipe is closed.

After a predetermined period has elapsed since the start of the separation operation, or after the degree of superheat of the non-azeotropic mixture refrigerant sucked by the compressor becomes less than a predetermined value, the on-off valve for the extraction pipe is closed Stop taking part of the non-azeotropic mixed refrigerant into the gas-liquid separator. Thus, the control for increasing the proportion of the low boiling point refrigerant in the non-azeotropic mixture refrigerant performing the refrigeration cycle can be stopped, and the operation can be continued with the composition of the non-azeotropic mixture refrigerant after the separation operation is performed. .
The “predetermined period” after a predetermined period has elapsed since the start of the separation operation is selected, for example, as the time until the desired mixing ratio is obtained by performing the separation operation.
As the “predetermined value” in which the degree of superheat of the refrigerant sucked by the compressor is less than the predetermined value, for example, a value set to avoid liquid compression of the compressor is used.

Furthermore, in the refrigeration apparatus according to one aspect of the present invention, the control unit opens and closes the outlet pipe when the outside air temperature is equal to or higher than a predetermined value or the temperature of the discharge gas discharged from the compressor is equal to or higher than a predetermined value. The valve is opened, the on-off valve for gas return piping is closed, and the on-off valve for liquid return piping is opened.

When the outside air temperature becomes equal to or higher than the predetermined value, there is no possibility of a problem such as frost formation on the evaporator. Therefore, when the outside air temperature becomes equal to or higher than a predetermined value, the on-off valve for gas return piping is closed to stop the low boiling point refrigerant from being preferentially returned during the refrigeration cycle. Then, the liquid return piping on-off valve is opened to return the high boiling point refrigerant, which is often present in the liquid phase portion, into the refrigeration cycle. At this time, by opening the on-off valve for the extraction pipe, the non-azeotropic mixed refrigerant is introduced from the refrigeration cycle to the gas-liquid separator, and the gas-liquid separation is performed in the gas-liquid separator By preferentially returning the boiling point refrigerant back to the refrigeration cycle, the proportion increase of the high boiling point refrigerant in the refrigeration cycle is promoted.
As described above, by performing the mixing operation of mixing the high boiling point refrigerant into the non-azeotropic mixture refrigerant performing the refrigeration cycle, the ratio of the high boiling point refrigerant in the non-azeotropic mixture refrigerant is increased, and the mixing at the time of refrigerant charge is performed. It can be returned to the percentage.
Further, when the temperature of the discharge gas discharged from the compressor becomes equal to or higher than a predetermined value, the discharge gas temperature can be lowered by returning the mixing ratio of the refrigerant at the time of the refrigerant filling by the mixing operation.

Furthermore, in the refrigeration system according to one aspect of the present invention, the control unit opens the on-off valve for the extraction pipe and opens the on-off valve for the gas return pipe during the cooling operation.

A low boiling point refrigerant such as R32 has a higher density than a high boiling point refrigerant such as R1234yf or R1234ze (E), and thus has a high COP. Therefore, at the time of the cooling operation, the ratio of the low boiling point refrigerant in the non-azeotropic mixed refrigerant which performs the refrigeration cycle is increased by performing the separation operation of opening the on-off valve for the extraction pipe and the on-off valve for the gas return pipe. Thereby, highly efficient cooling operation can be realized.

Furthermore, in the refrigeration apparatus according to one aspect of the present invention, the control unit opens the on-off valve for the extraction pipe when the temperature of the discharge gas discharged from the compressor reaches a predetermined value or more. The return piping on-off valve is closed, and the liquid return piping on-off valve is opened.

If the proportion of the low boiling point refrigerant in the non-azeotropic refrigerant mixture in which the refrigeration cycle is performed is high, the discharge gas temperature of the compressor may be excessively high. Therefore, when the discharge gas temperature exceeds a predetermined value, open the on-off valve for the extraction pipe, close the on-off valve for the gas return pipe, and perform the mixing operation to open the on-off valve for the liquid return pipe. Then, the proportion of the high-boiling point refrigerant in the non-azeotropic mixture refrigerant is increased to return to the mixing ratio at the time of refrigerant charging. As a result, by preventing the discharge gas temperature of the compressor from becoming excessively high, the equipment can be protected.

Further, a control method of a refrigeration apparatus according to one aspect of the present invention includes: a compressor for compressing a non-azeotropic refrigerant mixture in which low boiling point refrigerants having different boiling points and high boiling point refrigerant are mixed; A condenser for condensing non-azeotropic refrigerant, an expansion valve for expanding the non-azeotropic refrigerant led from the condenser, and an evaporator for evaporating the non-azeotropic refrigerant led from the expansion valve; A non-azeotropic mixture connected to a take-out pipe for taking out part of the non-azeotropic mixed refrigerant from between the condenser and the expansion valve, a take-off pipe on-off valve provided on the take-out pipe, and the take-out pipe A gas-liquid separator that stores refrigerant and separates gas-liquid, a gas return pipe that connects between the expansion valve and the evaporator, and a gas phase portion in the gas-liquid separator, and the gas return pipe A gas return valve provided between the expansion valve and the evaporator; A control method of a refrigeration apparatus comprising: a liquid return pipe for connecting a liquid phase portion in the vessel; and a liquid return pipe on / off valve provided on the liquid return pipe, comprising: the outlet pipe on / off valve; The on-off control of the gas return piping on-off valve and the liquid return piping on-off valve is performed.

The refrigerant that has been separated by the gas-liquid separator can be returned from the gas phase portion or the liquid phase portion into the refrigeration cycle simply by controlling each on-off valve of each pipe connected to the gas-liquid separator The mixing ratio of the non-azeotropic mixed refrigerant can be arbitrarily changed with the following configuration.
By separating the high-boiling point refrigerant from the non-azeotropic mixed refrigerant that performs the refrigeration cycle and performing the separation operation to increase the proportion of the low-boiling point refrigerant, the formation of frost on the evaporator is achieved by raising the saturation temperature in the evaporator. It can be suppressed.
During the cooling operation, the separation operation is performed by opening the on-off valve for the extraction pipe and the on-off valve for the gas return pipe to increase the ratio of the low boiling point refrigerant in the non-azeotropic mixed refrigerant performing the refrigeration cycle. Efficient cooling operation can be realized.

It is a refrigerant circuit of a refrigerating apparatus concerning one embodiment of the present invention, and is a schematic structure figure showing normal operation (enclosed composition) at the time of heating operation. It is a schematic block diagram of the refrigerant circuit which showed separation operation at the time of heating operation. It is a schematic block diagram of the refrigerant circuit which showed normal operation (separation composition) at the time of heating operation. It is a schematic block diagram of the refrigerant circuit which showed the mixing operation at the time of heating operation. It is the flowchart which showed the control at the time of heating operation. It is a schematic block diagram of the refrigerant circuit which showed normal operation (enclosed composition) at the time of air conditioning operation. It is a schematic block diagram of the refrigerant circuit which showed separation operation at the time of air conditioning operation. It is a schematic block diagram of the refrigerant circuit which showed normal operation (separation composition) at the time of air conditioning operation. It is a schematic block diagram of the refrigerant circuit which showed the mixing operation at the time of air conditioning operation. It is the flowchart which showed the control at the time of air conditioning operation. It is ap (pressure)-h (enthalpy) diagram which showed the temperature slip of a non-azeotropic mixture refrigerant. It is the graph which showed the temperature slip according to the mixing ratio of the non-azeotropic mixture refrigerant | coolant, and showed the temperature slip at the time of saturation temperature 40 degreeC. The temperature slip according to the mixing ratio of the non-azeotropic mixture refrigerant is shown, which is the temperature slip when the saturation temperature is 10 ° C. It is the graph which showed the change of COP according to the mixing ratio of the non-azeotropic mixture refrigerant.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.
FIG. 1 shows a refrigerant circuit configuration of the refrigeration apparatus 1 of the present embodiment. The refrigeration apparatus 1 is used, for example, as an air conditioner, and can perform heating operation and cooling operation by switching a four-way valve (not shown) provided on the discharge side of the compressor 3. FIG. 1 shows the configuration during heating operation.

The refrigerating apparatus 1 uses, as a refrigerant, a non-azeotropic mixed refrigerant in which R32 and R1234ze (E) are mixed. R32 is considered as a low boiling point refrigerant having a low boiling point relative to R1234ze (E). R1234ze (E) is regarded as a high boiling point refrigerant having a high boiling point relative to R32. Note that R1234yf may be used instead of R1234ze (E).

The refrigeration system 1 includes a compressor 3 that compresses a non-azeotropic mixture refrigerant (hereinafter sometimes simply referred to as “refrigerant”), a condenser 5, an expansion valve 7, and an evaporator 9. By connecting the compressor 3, the condenser 5, the expansion valve 7, and the evaporator 9 with a refrigerant pipe, a refrigerant circuit that performs a refrigeration cycle is configured.

The compressor 3 is installed inside the outdoor unit, for example, a scroll compressor or a rotary compressor, and is driven by an electric motor (not shown). The electric motor is provided with an inverter device, and the number of rotations is arbitrarily changed by a command from a control unit (not shown).
A suction pressure sensor 11 for measuring the suction pressure Ps of the refrigerant is provided on the suction side of the compressor 3, and a discharge temperature sensor 13 for measuring the discharge temperature of the refrigerant is provided on the discharge side of the compressor 3. ing. The outputs of the suction pressure sensor 11 and the discharge temperature sensor 13 are sent to the control unit.

The condenser 5 is an indoor heat exchanger, and heats and exchanges heat with room air during heating operation to condense the high-pressure gas refrigerant introduced from the compressor 3.
The expansion valve 7 expands the refrigerant condensed and liquefied in the condenser 5. The opening degree of the expansion valve 7 is controlled by the control unit.
The evaporator 9 is an outdoor heat exchanger installed inside the outdoor unit, and during the heating operation, the evaporator 9 evaporates the refrigerant expanded by the expansion valve 7 by exchanging heat with the outside air as the outdoor heat exchanger. . At the refrigerant outlet of the evaporator 9, an evaporator outlet temperature sensor 15 for measuring the temperature of the evaporating refrigerant is provided. The output of the evaporator outlet temperature sensor 15 is sent to the control unit.

A gas-liquid separator 17 is provided separately from the main refrigerant circuit that performs the refrigeration cycle by the compressor 3, the condenser 5, the expansion valve 7 and the evaporator 9 described above. The gas-liquid separator 17 is a tank having a capacity capable of temporarily storing the refrigerant. The gas-liquid separator 17 is installed inside an outdoor unit that accommodates the compressor 3 and the evaporator 9.

A discharge pipe 19 is provided between the discharge position A between the condenser 5 and the expansion valve 7 and the upper portion of the gas-liquid separator 17. The outlet pipe 19 is provided with an outlet pipe on-off valve 20. The outlet piping on-off valve 20 is, for example, a solenoid valve, and is opened and closed in accordance with a command from the control unit.

A gas return pipe 21 is provided between a joining position B between the expansion valve 7 and the evaporator 9 and the gas-liquid separator 17. The upstream end 21 a of the gas return pipe 21 is located at the upper part of the gas-liquid separator 17 and opens to the gas phase portion of the refrigerant separated in the gas-liquid separator 17. The gas return pipe 21 is provided with a gas return pipe on-off valve 22. The gas return piping on-off valve 22 is, for example, an electromagnetic valve, which is opened and closed in accordance with a command from the control unit.

A liquid return pipe 23 is provided between the gas-liquid separator 17 and a joining position B between the expansion valve 7 and the evaporator 9. The upstream end 23 a of the liquid return pipe 23 is located at the lower portion (or the bottom) of the gas-liquid separator 17 and opens to the liquid phase portion of the refrigerant separated in the gas-liquid separator 17. The liquid return pipe 23 is provided with a liquid return pipe on-off valve 24. The liquid return piping on-off valve 24 is, for example, an electromagnetic valve, and is opened and closed in accordance with a command from the control unit.

The control unit is configured of, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a computer readable storage medium, and the like. Then, a series of processes for realizing various functions are stored in the form of a program, for example, in a storage medium or the like in the form of a program, and the CPU reads this program into a RAM or the like to execute information processing and arithmetic processing. Thus, various functions are realized. The program may be installed in advance in a ROM or other storage medium, may be provided as stored in a computer-readable storage medium, or may be distributed via a wired or wireless communication means. Etc. may be applied. The computer readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory or the like.

<Heating operation>
Next, an operation mode during heating operation of the refrigeration apparatus 1 configured as described above will be described.
[Normal operation (enclosed composition): heating operation]
FIG. 1 shows a normal operation (enclosed composition) at the time of heating operation. This normal operation is operated with a composition having a mixing ratio equivalent to that when the non-azeotropic mixed refrigerant is enclosed in the refrigeration system 1 (for example, a mixing ratio of R32: R1234ze (E) = 1: 1). .

The outlet piping on-off valve 20 is closed, the gas return piping on-off valve 22 is open, and the liquid return piping on-off valve 24 is open. In each of the drawings, the open valve is displayed as white and the closed valve is displayed as solid.

By closing the outlet piping on-off valve 20, the refrigerant is not extracted from the inside of the refrigeration cycle, and the mixing ratio of the refrigerant performing the refrigeration cycle is not changed. Further, by opening the on / off valve 24 for liquid return piping, the liquid refrigerant is not stored in the gas-liquid separator 17, and the mixing ratio of the refrigerant performing the refrigeration cycle is not changed.
The gas return piping on-off valve 22 is opened to equalize the pressure with the refrigerant pressure after being expanded by the expansion valve 7. This makes it possible to prevent the low boiling point refrigerant from remaining unvaporized during normal operation, and to prevent the liquid seal state in which the inside of the gas-liquid separator 17 is filled with unvaporized refrigerant during stoppage It is for.

[Separate operation (during heating operation)]
FIG. 2 shows the separation operation at the time of heating operation. The separation operation is performed after the above-described normal operation (encapsulation composition), and R32 (low boiling point refrigerant) in the refrigerant performing the refrigeration cycle by separating R1234ze (high boiling point refrigerant) from the refrigerant performing the refrigeration cycle Operation to increase the mixing ratio of

The outlet piping on-off valve 20 is open, the gas return piping on-off valve 22 is open, and the liquid return piping on-off valve 24 is closed.

By opening the on-off valve 20 for the extraction pipe, a portion of the liquid refrigerant is introduced into the gas-liquid separator 17 from between the condenser 5 and the expansion valve 7. Since the gas return piping on-off valve 22 is open in the gas-liquid separator 17 and the pressure is low equivalent to the pressure between the expansion valve 7 and the evaporator 9, the inside of the gas-liquid separator 17 is The low-boiling-point refrigerant R32 led to is preferentially evaporated over the high-boiling-point refrigerant R1234ze (E). Then, R 32 evaporated in the gas-liquid separator 17 passes through the gas return pipe 21 and is returned from the joining position B to the evaporator 9 to be used as a refrigerant that performs a refrigeration cycle. Thereby, the mixing ratio of R32 in the refrigerant performing the refrigeration cycle is increased.

[Normal operation (separated composition): heating operation]
FIG. 3 shows a normal operation (separated composition) at the time of heating operation. This normal operation is performed after the above-described separation operation, and is operated in a separated composition in which R1234ze (E) in the refrigerant performing the refrigeration cycle is separated to increase the mixing ratio of R32 It is.

The outlet piping on-off valve 20 is closed, the gas return piping on-off valve 22 is open, and the liquid return piping on-off valve 24 is closed.

By closing the outlet piping on-off valve 20, the refrigerant is not extracted from the inside of the refrigeration cycle, and the mixing ratio of the refrigerant performing the refrigeration cycle is not changed. Further, by closing the liquid return piping on-off valve 24, the liquid refrigerant in the gas-liquid separator 17 is not returned to the refrigeration cycle, and the mixing ratio of the refrigerant performing the refrigeration cycle is not changed.
The gas return piping on-off valve 22 is opened to lead R 32 separated in the gas-liquid separator 17 to the evaporator 9 through the gas return piping 21.

[Mixed operation: heating operation]
FIG. 4 shows the mixing operation at the time of heating operation. The mixing operation is performed after the above-described normal operation (separation composition), and is performed to mix R1234ze (E) into the refrigerant performing the refrigeration cycle to reduce the mixing ratio of R32 in the refrigerant.

The outlet piping on-off valve 20 is open, the gas return piping on-off valve 22 is closed, and the liquid return piping on-off valve 24 is open.

By opening the on-off valve 20 for the extraction pipe, liquid refrigerant is introduced into the gas-liquid separator 17 from between the condenser 5 and the expansion valve 7. In the gas-liquid separator 17, since the gas return piping on-off valve 22 is closed, R32 evaporated in the gas-liquid separator 17 is not supplied from the joining position B to the refrigerant performing the refrigeration cycle. . On the other hand, since the liquid return piping on-off valve 24 is opened, the liquid refrigerant stored in the gas-liquid separator 17 is led from the junction position B to the evaporator 9 through the liquid return piping 23. As a result, the liquid refrigerant in the gas-liquid separator 17 in which R1234ze (E) is concentrated by the separation operation (see FIG. 2) is returned to the refrigerant performing the refrigeration cycle, so R1234ze (E in the refrigerant performing the refrigeration cycle The mixing ratio of) increases.

Next, a control method of the refrigeration system 1 during the heating operation will be described using FIG. 5. Each step shown below is performed by instructions from the control unit.

When the operation is started, it is determined whether the outside air temperature is less than a predetermined value (for example, 10 ° C.) (step S1). As the outside air temperature, a measurement value of an outside air temperature sensor (not shown) is used. When the outside air temperature is less than 10 ° C., the separation operation (see FIG. 2) is performed to increase the mixing ratio of R32 in the refrigerant that performs the refrigeration cycle. Thereby, the temperature slip in the evaporator 9 is reduced (see FIG. 12B), and the low pressure in the evaporator 9 is increased to prevent frost formation.

If it is determined in step S1 that the outside air temperature is 10 ° C. or higher, the process proceeds to step S3 and a normal operation (enclosed composition) is performed (see FIG. 1). In normal operation (enclosed composition), the mixing ratio in the refrigerant performing the refrigeration cycle is equal to that in the refrigerant filling, and the mixing ratio of R32 is not excessively large, so the discharge gas temperature of the refrigerant gas discharged from the compressor 3 Is maintained below a predetermined value.

If the measured temperature Tho-R of the evaporator outlet temperature sensor 15 is equal to or higher than a predetermined value (for example, -3 ° C.) while performing the normal operation (enclosed composition) in step S3 (step S4), the unit is stopped It is determined whether or not there is a command (step S5). When a unit stop command is issued, the refrigeration system 1 is stopped and the process is ended. If the unit stop command has not been issued, the process returns to step S3 and the normal operation (enclosed composition) is continued.
When the measured temperature Tho-R of the evaporator outlet temperature sensor 15 becomes lower than -3 ° C. in step S4, the process proceeds to step S3 and the separation operation is performed. By the separation operation, the low pressure of the evaporator 9 rises to prevent frost formation.

While performing the separation operation in step S2, it is determined whether the degree of suction superheat of the compressor 3 is less than 2 ° C. or whether a predetermined time (for example, one hour) has passed since the separation operation was started ( Step S6). The suction superheat degree is calculated from the difference between the saturation temperature of the pressure obtained by the suction pressure sensor 11 and the temperature obtained by the evaporator outlet temperature sensor 15.

In step S6, when the degree of suction superheat is not less than 2 ° C. and one hour has not elapsed from the separation operation, the process returns to step S2 and the separation operation is continued.

In step S6, when the degree of suction superheat becomes less than 2 ° C., or when one hour or more has passed from the separation operation, the process proceeds to step S7, and the normal operation (separation composition) is performed (see FIG. 3). In the normal operation (separation composition), an operation is performed in which R1234ze (E) is separated from the refrigerant performing the refrigeration cycle to increase the mixing ratio of R32. As a result, frost formation on the evaporator 9 is suppressed and, as shown in FIG. 13, an operation with a high COP is performed.

While performing the normal operation (separation composition), it is determined whether the discharge temperature Tho-D measured by the discharge temperature sensor 13 exceeds a predetermined value (for example, 110 ° C.) (step S8). If the discharge temperature Tho-D exceeds 110 ° C., the process proceeds to step S9 to perform the mixing operation (see FIG. 4). In the mixing operation, R1234ze (E) is mixed in the refrigerant that performs the refrigeration cycle, and is operated to approach the mixing ratio at the time of sealing. As a result, the mixing ratio of R32 in the refrigerant that performs the refrigeration cycle decreases, and the discharge temperature decreases. The mixing operation ends after a predetermined time (for example, 5 minutes) elapses, and the process proceeds to step S3 and a normal operation (enclosed composition) is performed.

If the discharge temperature Tho-D does not exceed 110 ° C. in step S8, the process proceeds to step S10, and it is determined whether there is a unit stop command. If the unit stop command has not been issued, the process returns to step S7 and the normal operation (separated composition) is continued. If a unit stop command is issued, the process proceeds to step S11, and after performing a mixing operation for a predetermined time (for example, 5 minutes), the refrigeration apparatus 1 is stopped and the process is ended. By performing the mixing operation before stopping the refrigeration system 1, the mixing ratio in the refrigerant that performs the refrigeration cycle at the next activation is returned at the time of refrigerant charging.

<During cooling operation>
Next, an operation mode at the time of cooling operation of the refrigeration apparatus 1 configured as described above will be described. In the cooling operation, the four-way valve (not shown) provided on the discharge side of the compressor 3 is switched to change the heating operation. Thereby, the condenser switches to the evaporator (indoor heat exchanger) during the cooling operation during the heating operation, and switches to the condenser (the outdoor heat exchanger) during the cooling operation.

[Normal operation (enclosed composition): During cooling operation]
FIG. 6 shows a normal operation (enclosed composition) at the time of the cooling operation. This normal operation is operated with a composition having a mixing ratio equivalent to that when the non-azeotropic mixed refrigerant is enclosed in the refrigeration system 1 (for example, a mixing ratio of R32: R1234ze (E) = 1: 1). .

By closing the outlet piping on-off valve 20, the refrigerant is not extracted from the inside of the refrigeration cycle, and the mixing ratio of the refrigerant performing the refrigeration cycle is not changed. Further, by opening the on-off valve 24 for liquid return piping, the liquid refrigerant is not stored in the gas-liquid separator 17, and the mixing ratio of the refrigerant forming the refrigeration cycle is not changed.
The gas return piping on-off valve 22 is opened to equalize the pressure with the refrigerant pressure after being expanded by the expansion valve 7. This makes it possible to prevent the low boiling point refrigerant from remaining unvaporized during normal operation, and to prevent the liquid seal state in which the inside of the gas-liquid separator is filled with unvaporized refrigerant during stoppage It is.

[Separate operation (during cooling operation)]
FIG. 7 shows the separation operation at the time of the cooling operation. The separation operation is performed after the above-described normal operation (enclosed composition), and R32 (low) in the refrigerant performing the refrigeration cycle by separating R1234ze (E) (high boiling point refrigerant) from the refrigerant performing the refrigeration cycle The operation is to increase the mixing ratio of the boiling point refrigerant).

By opening the on-off valve 20 for the extraction pipe, liquid refrigerant is introduced into the gas-liquid separator 17 from between the condenser 5 and the expansion valve 7. Since the gas return piping on-off valve 22 is open in the gas-liquid separator 17 and the pressure is low equivalent to the pressure between the expansion valve 7 and the evaporator 9, the inside of the gas-liquid separator 17 is The low-boiling-point refrigerant R32 led to is preferentially evaporated over the high-boiling-point refrigerant R1234ze (E). Then, R 32 evaporated in the gas-liquid separator 17 passes through the gas return pipe 22 and is returned from the joining position B to the evaporator 9 and is used as a refrigerant that performs a refrigeration cycle. Thereby, the mixing ratio of R32 in the refrigerant performing the refrigeration cycle is increased.

[Normal operation (separated composition): During cooling operation]
FIG. 8 shows a normal operation (separated composition) at the time of the cooling operation. This normal operation is performed after the above-described separation operation, and is operated in a separated composition in which R1234ze (E) in the refrigerant performing the refrigeration cycle is separated to increase the mixing ratio of R32 It is.

The outlet piping on-off valve 20 is closed, the gas return piping on-off valve 22 is closed, and the liquid return piping on-off valve 24 is closed.

By closing the outlet piping on-off valve 20, the refrigerant is not extracted from the inside of the refrigeration cycle, and the mixing ratio of the refrigerant performing the refrigeration cycle is not changed. Further, by closing the liquid return piping on-off valve 24, the liquid refrigerant in the gas-liquid separator 17 is not returned to the refrigeration cycle, and the mixing ratio of the refrigerant performing the refrigeration cycle is not changed.

Unlike the normal operation (separated composition) during the heating operation shown in FIG. 3, the gas return piping on-off valve 22 is closed. Since the outside air temperature is higher in the cooling operation than in the heating operation, the environmental temperature in the outdoor unit in which the gas-liquid separator 17 is installed is high, and R1234ze (E), which is a high boiling point refrigerant, also evaporates. This is because there is a possibility that the refrigerant may join the refrigerant performing the refrigeration cycle through the return pipe 21. When the gas-liquid separator 17 is installed in an environment (for example, indoor) which is not affected by the outside air temperature than in the outdoor unit, it is for gas return piping as in the normal operation (separation composition) during heating operation. The on-off valve 22 may be opened.

[Mixing operation: During cooling operation]
FIG. 9 shows the mixing operation at the time of the cooling operation. The mixing operation is performed after the above-described normal operation (separation composition), and is performed to mix R1234ze (E) into the refrigerant performing the refrigeration cycle to reduce the mixing ratio of R32 in the refrigerant.

By opening the on-off valve 20 for the extraction pipe, liquid refrigerant is introduced into the gas-liquid separator 17 from between the condenser 5 and the expansion valve 7. In the gas-liquid separator 17, since the gas return piping on-off valve 22 is closed, R32 evaporated in the gas-liquid separator 17 is not supplied from the joining position B to the refrigerant performing the refrigeration cycle. . On the other hand, since the liquid return piping on-off valve 24 is opened, the liquid refrigerant stored in the gas-liquid separator 17 is led from the junction position B to the evaporator 9 through the liquid return piping 23. As a result, the liquid refrigerant in the gas-liquid separator 17 in which R1234ze (E) is concentrated by the separation operation (see FIG. 7) is returned to the refrigerant that performs the refrigeration cycle, so R1234ze (E in the refrigerant that performs the refrigeration cycle The mixing ratio of) increases.

Next, a control method of the refrigeration apparatus 1 during the cooling operation will be described using FIG. Each step shown below is performed by instructions from the control unit.

When the operation is started, the process proceeds to step S21, the separation operation (see FIG. 7) is performed, and the mixing ratio of R32 in the refrigerant performing the refrigeration cycle is increased. Thus, the cooling operation with improved COP is performed (see FIG. 13).

While performing the separation operation in step S21, it is determined whether the degree of suction superheat of the compressor 3 is less than 2 ° C. or whether a predetermined time (for example, one hour) has passed since the separation operation was started ( Step S22).

If it is determined in step S22 that the degree of suction superheat is not less than 2 ° C. and one hour has not elapsed from the separation operation, the process returns to step S21 to continue the separation operation.

In step S22, when the degree of suction superheat is less than 2 ° C. or one hour or more has elapsed from the separation operation, the process proceeds to step S23, and the normal operation (separation composition) is performed (see FIG. 8). In the normal operation (separation composition), an operation is performed in which R1234ze (E) is separated from the refrigerant performing the refrigeration cycle to increase the mixing ratio of R32. Thus, the cooling operation with a high COP is continued.

While performing the normal operation (separation composition) in step S23, it is determined whether the discharge temperature Tho-D measured by the discharge temperature sensor 13 exceeds a predetermined value (for example, 110 ° C.) (step S24). If the discharge temperature Tho-D exceeds 110 ° C., the process proceeds to step S25 to perform the mixing operation (see FIG. 9). In the mixing operation, R1234ze (E) is mixed in the refrigerant that performs the refrigeration cycle, and is operated to approach the mixing ratio at the time of sealing. As a result, the mixing ratio of R32 in the refrigerant that performs the refrigeration cycle decreases, and the discharge temperature decreases. The mixing operation is finished after a predetermined time (for example, 5 minutes) elapses, and the process proceeds to step S26 where a normal operation (enclosed composition) is performed (see FIG. 6).

In normal operation (enclosed composition), the mixing ratio in the refrigerant performing the refrigeration cycle is equal to that at the time of refrigerant charging, and the mixing ratio of R32 is not large, so the discharge gas temperature of the refrigerant gas discharged from the compressor 3 is predetermined. It becomes the operation kept below the value.

While performing the normal operation (enclosed composition) in step S26, it is determined whether or not there is a unit stop command (step S27). When a unit stop command is issued, the refrigeration system 1 is stopped and the process is ended. If the unit stop command has not been issued, the process returns to step S26 and the normal operation (enclosed composition) is continued.

If it is determined in step S24 that the discharge temperature Tho-D does not exceed 110 ° C., the process proceeds to step S28, and it is determined whether there is a unit stop instruction. If the unit stop command has not been issued, the process returns to step S23 and the normal operation (separation composition) is continued. If a unit stop command has been issued, the process proceeds to step S29, and after performing a mixing operation for a predetermined time (for example, 5 minutes), the refrigeration apparatus 1 is stopped and the process is ended. By performing the mixing operation before stopping the refrigeration system 1, the mixing ratio in the refrigerant that performs the refrigeration cycle at the next activation is returned at the time of refrigerant charging.

As described above, according to the present embodiment, the following effects can be obtained.
The gas refrigerant or liquid refrigerant separated by the gas / liquid separator 17 is subjected to a refrigeration cycle only by connecting the

pipes

19, 21 and 23 to the gas / liquid separator 17 and controlling the on / off

valves

20, 22 and 24. Since it can be returned to the inside, the mixing ratio of the low boiling point refrigerant (R32) and the high boiling point refrigerant (R1234ze (E)) can be arbitrarily changed by a simple configuration.

During the heating operation, the temperature of the evaporator 9 is low because the outside air temperature is generally low. When the temperature of the evaporator 9 falls below a predetermined value, for example, the evaporator may be frosted. Therefore, when the outside air temperature is less than a predetermined value (for example, 10 ° C.) or the evaporator outlet temperature is less than a predetermined value (for example, -3 ° C.), the gas return piping on-off valve 22 is opened to perform refrigeration. Increase the proportion of R32 (low-boiling point refrigerant) in the cycle. At this time, by opening the on-off valve 20 for the extraction pipe, the refrigerant is introduced from the refrigeration cycle to the gas-liquid separator 17, and the gas-liquid separation is performed in the gas-liquid separator 17 to perform R32 during the refrigeration cycle. Reversion further promotes the increase in the proportion of R32 in the refrigeration cycle. By performing such separation operation (see FIG. 2), temperature slip can be achieved by performing separation operation in which R1234ze (E) (high boiling point refrigerant) is separated from the refrigerant performing the refrigeration cycle to increase the ratio of R32. It is possible to reduce the size and increase the saturation temperature in the evaporator 9 to suppress frost formation.

After the separation operation (see FIG. 2) is performed, after the predetermined period (for example, 1 hour) elapses, or after the degree of suction superheat becomes less than the predetermined value (for example, 2 ° C.), the extraction pipe on-off valve 20 is closed. Thus, the removal of part of the refrigerant that performs the refrigeration cycle into the gas-liquid separator 17 is stopped (see FIG. 3). As a result, the control for increasing the ratio of R32 in the refrigerant that performs the refrigeration cycle is stopped, and the normal operation (separation composition) can be performed with the composition of the mixed refrigerant after the separation operation.

When the outside air temperature becomes equal to or higher than a predetermined value (for example, 10 ° C.) during the heating operation, there is no possibility of a defect such as frost formation on the evaporator 9. Therefore, when the outside air temperature becomes equal to or higher than the predetermined value, the gas return piping on-off valve 22 is closed to stop that R32 is preferentially returned during the refrigeration cycle. Then, the liquid return piping on-off valve 24 is opened to return R1234ze (E), which is mostly present in the liquid refrigerant in the gas-liquid separator 17, back to the refrigeration cycle. At this time, by opening the on-off valve 20 for the extraction pipe, the refrigerant is introduced from the refrigeration cycle to the gas-liquid separator 17, and the gas-liquid separation is performed in the gas-liquid separator 17 to obtain R1234ze (liquid phase). E) By bringing the E cycle into the refrigeration cycle preferentially, it promotes an increase in the proportion of R1234ze (E) in the refrigeration cycle.
Thus, by performing the mixing operation of mixing R1234ze (E) into the refrigerant that performs the refrigeration cycle, the ratio of R1234ze (E) in the refrigerant can be increased, and the mixing ratio at the time of refrigerant charging can be returned to .
In addition, when the discharge gas temperature discharged from the compressor 3 reaches a predetermined value (for example, 110 ° C.) or more, the discharge gas temperature is lowered by returning the mixing ratio of the refrigerant at the time of refrigerant filling by the mixing operation. Can.

During the cooling operation, the ratio R32 in the refrigerant performing the refrigeration cycle is increased by performing the separation operation (see FIG. 7) in which the on-off valve 20 for the extraction pipe and the on-off valve 22 for the gas return pipe are opened. Thereby, highly efficient cooling operation can be realized.

Even in the cooling operation, when the discharge gas temperature reaches a predetermined value (for example, 110 ° C.), the outlet piping on-off valve 20 is opened and the gas return piping on-off valve 22 is closed to use for liquid return piping. By performing a mixing operation (see FIG. 9) in which the on-off valve 24 is opened, the ratio of R1234ze (E) in the refrigerant is increased to return to the mixing ratio at the time of refrigerant filling. By this, by preventing the discharge gas temperature of the compressor 3 from becoming excessively high, the equipment can be protected.

In the embodiment described above, the refrigeration apparatus capable of switching between heating and cooling has been described, but the present invention is not limited to this, and is also applied to a refrigeration apparatus performing only heating operation or only cooling operation. be able to.

DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus 3 Compressor 5 Condenser 7 Expansion valve 9 Evaporator 11 Suction pressure sensor 13 Discharge temperature sensor 15 Evaporator outlet temperature sensor 17 Gas-liquid separator 19 Extraction piping 20 Extraction piping on-off valve 21 Gas return piping 22 Gas return Piping on-off valve 23 Liquid return piping 24 Liquid return piping on-off valve A Extraction position B Merging position

Claims

A compressor for compressing a non-azeotropic refrigerant mixture in which low-boiling refrigerants and high-boiling refrigerants having different boiling points are mixed;
A condenser for condensing the non-azeotropic mixed refrigerant introduced from the compressor;
An expansion valve for expanding the non-azeotropic mixed refrigerant introduced from the condenser;
An evaporator for evaporating the non-azeotropic mixed refrigerant introduced from the expansion valve;
An extraction pipe for extracting a part of the non-azeotropic refrigerant mixture from between the condenser and the expansion valve;
A release piping on-off valve provided in the removal piping;
A gas-liquid separator connected to the take-out pipe for storing non-azeotropic mixed refrigerant for gas-liquid separation;
A gas return pipe connecting between the expansion valve and the evaporator and a gas phase portion in the gas-liquid separator;
A gas return piping on-off valve provided in the gas return piping;
A liquid return pipe that connects between the expansion valve and the evaporator and a liquid phase portion in the gas-liquid separator;
A liquid return piping on-off valve provided in the liquid return piping;
A control unit that controls the open / close valve for the extraction pipe, the open / close valve for the gas return pipe, and the open / close valve for the liquid return pipe;
A refrigeration system equipped with
The control unit opens the on-off valve for the extraction pipe and opens the on-off valve for the gas return pipe when the outside air temperature is lower than a predetermined value or the temperature of the evaporator is lower than the predetermined value during heating operation. The refrigeration apparatus according to claim 1, wherein a separation operation is performed to return the gas refrigerant separated by the gas-liquid separator from the gas return pipe to the evaporator side.
The control unit closes the on-off valve for the extraction pipe after a predetermined period has elapsed since the start of the separation operation, or after the degree of superheat of the non-azeotropic mixed refrigerant sucked by the compressor becomes less than a predetermined value. The refrigeration apparatus according to claim 2, wherein
When the outside air temperature is equal to or higher than a predetermined value or the temperature of the discharge gas discharged from the compressor is equal to or higher than a predetermined value, the control unit opens the on-off valve for the extraction pipe and opens the on-off valve for the gas return pipe. The refrigeration apparatus according to claim 2 or 3, wherein the liquid return pipe on-off valve is opened by closing the liquid return pipe.
The refrigeration apparatus according to claim 1, wherein the control unit opens the on-off valve for extraction piping and opens the on-off valve for gas return piping during cooling operation.
When the temperature of the discharge gas discharged from the compressor reaches a predetermined value or more, the control unit opens the on-off valve for the extraction pipe and closes the on-off valve for the gas return pipe, and the liquid return pipe The refrigeration apparatus according to claim 4, wherein the on-off valve is opened.
A compressor for compressing a non-azeotropic refrigerant mixture in which low-boiling refrigerants and high-boiling refrigerants having different boiling points are mixed;
A condenser for condensing the non-azeotropic mixed refrigerant introduced from the compressor;
An expansion valve for expanding the non-azeotropic mixed refrigerant introduced from the condenser;
An evaporator for evaporating the non-azeotropic mixed refrigerant introduced from the expansion valve;
An extraction pipe for extracting a part of the non-azeotropic refrigerant mixture from between the condenser and the expansion valve;
A release piping on-off valve provided in the removal piping;
A gas-liquid separator connected to the take-out pipe for storing non-azeotropic mixed refrigerant for gas-liquid separation;
A gas return pipe connecting between the expansion valve and the evaporator and a gas phase portion in the gas-liquid separator;
A gas return piping on-off valve provided in the gas return piping;
A liquid return pipe that connects between the expansion valve and the evaporator and a liquid phase portion in the gas-liquid separator;
A liquid return piping on-off valve provided in the liquid return piping;
A control method of a refrigeration system provided with
A control method of a refrigeration system which performs opening and closing control of the on-off valve for extraction piping, the on-off valve for gas return piping, and the on-off valve for liquid return piping.