JP6692715B2 - Refrigeration apparatus and control method thereof - Google Patents

Description

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

  An HFC refrigerant such as R410A is used as the refrigerant used in the air conditioner. However, the HFC refrigerant represented by R410A has a high GWP (global warming potential). Therefore, among HFC refrigerants, R32 having a lower GWP than R410A, and HFO refrigerants 1234yf and R1234ze (E) are listed as candidates for the next-generation refrigerant for R410A. However, due to the physical properties of CFC refrigerants and natural refrigerants, there are merits and demerits in refrigerants that are candidates for the next period. For example, R32 has a lower GWP than R410A and can obtain the same or higher performance, but has a drawback that it has a higher discharge temperature and lower reliability in a low temperature range than R410A. R1234yf and R1234ze (E) have the advantage that GWP with GWP of 10 or less is low, but since they have a lower density than R410A, they have only about 50% volume capacity, and in order to ensure equivalent performance. There is a drawback in that the size of the device is increased.

  In order to supplement such advantages and disadvantages of the refrigerant, use of a mixed refrigerant in which two or more kinds of refrigerants are mixed is being studied. Patent Document 1 below discloses that the ratio of the mixed refrigerant in the refrigeration cycle is changed by dissolving the mixed refrigerant in the refrigerating machine 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 a temperature slip as shown in FIG. That is, since the boiling points and the condensation points of the mixed refrigerants are different, the isotherm in the wet steam (between the saturated liquid line and the saturated vapor line) does not have a constant pressure (p) like a single refrigerant, and p -It is an isotherm that descends to the right on the h diagram. That is, a temperature slip occurs in the non-azeotropic mixed refrigerant.

  Further, the temperature difference of the temperature slip varies depending on the proportion of each refrigerant in the non-azeotropic mixed refrigerant, as shown in FIG. 12, for example. 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. 12 (a): saturation temperature 40). (° C) and the temperature difference [° C] of the temperature slip on the low pressure side (Fig. 12 (b): saturation temperature 10 ° C). As can be seen from the figure, the temperature slip becomes maximum when the mixing ratio of R32 to R1234ze (E) is about 20 wt%. In this case, since the saturation temperature is set to 10 ° C. on the low pressure side, the low temperature side, that is, the evaporator temperature may be 0 ° C. or less, and thus frost may be formed on the evaporator. During heating operation, when the evaporator is frosted, the heat exchange performance is reduced and the amount of heat absorption is reduced, so that the heating performance is significantly reduced.

  FIG. 13 shows the COP (coefficient of performance) during the cooling operation and the 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 with respect to R1234ze (E), the horizontal axis (upper axis) is the GWP at each mixing ratio, and the vertical axis is R410A. COP in the same capacity ratio to. As can be seen from the figure, when the R32 mixing ratio decreases, the ratio of R1234ze (E) increases, so the GWP decreases, but the COP during the cooling operation and the heating operation decreases, and particularly the COP decrease during the cooling operation is large. ..

  Therefore, it is desired to change the mixing ratio of the non-azeotropic mixed refrigerant that performs the refrigeration cycle during operation. In Patent Document 1 described above, the ratio of the mixed refrigerant in the refrigeration cycle can be changed, but since the solubility of the refrigerant in the refrigerating machine oil is used, it is necessary to control the temperature of the refrigerating machine oil and the amount of stored oil. May be complicated.

The present invention has been made in view of such circumstances, and provides a refrigerating apparatus and a control method thereof that can change the mixing ratio of a non-azeotropic mixed refrigerant that performs a refrigerating cycle with a simple configuration during operation. With the goal.
Another object of the present invention is to provide a refrigerating apparatus and a control method thereof that can prevent the evaporator temperature from frosting due to the temperature slip of the non-azeotropic mixed refrigerant.
Another object of the present invention is to provide a refrigerating apparatus using a non-azeotropic mixed refrigerant and a control method thereof, which can suppress performance deterioration during cooling operation as much as possible.

In order to solve the above problems, the refrigerating apparatus and the control method thereof according to the present invention employ the following means.
That is, the refrigeration apparatus according to the present invention, a compressor for compressing a non-azeotropic mixed refrigerant in which a low boiling point refrigerant and a high boiling point refrigerant having different boiling points are mixed, and a non-azeotropic mixed refrigerant introduced from the compressor. A condenser for condensing, 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, the condenser and the expansion A take-out pipe for taking out a part of the non-azeotropic mixed refrigerant from between the valve, a take-out pipe opening / closing valve provided in the take-out pipe, and a pipe connected to the take-out pipe to store the non-azeotropic mixed refrigerant and store the gas. A gas-liquid separator for liquid separation, connecting between the expansion valve and the evaporator and a gas phase portion in the gas- liquid separator, of the non-azeotropic mixed refrigerant separated by the gas-liquid separator a gas return pipe returning the gas refrigerant into between the gas phase and the expansion valve and the evaporator, said A gas return pipe opening / closing valve provided in the return pipe, a liquid return pipe connecting between the expansion valve and the evaporator and a liquid phase portion in the gas-liquid separator, and the liquid return pipe. An on-off valve for the liquid return pipe, a control unit for controlling the on-off valve for the extraction pipe, the on-off valve for the gas return pipe, and the on-off valve for the liquid return pipe are provided.

By opening the extraction pipe on-off valve according to a command from the control unit, a portion of the non-azeotropic mixed refrigerant is taken out from between the condenser and the expansion valve via the extraction pipe, and is temporarily stored in the gas-liquid separator. Store. In the gas-liquid separator, gas-liquid is separated according to the temperature and pressure in the gas-liquid separator, and a liquid phase part and a gas phase part are formed.
When the on-off valve for the gas return pipe is opened according to a command from the control unit, the expansion valve and the evaporator are communicated with the gas phase part of the gas-liquid separator via the gas return pipe, and the inside of the gas phase part becomes low pressure. Then, the low boiling point refrigerant is preferentially introduced to the evaporator. As a result, the proportion of the low boiling point refrigerant in the non-azeotropic mixed refrigerant performing the refrigeration cycle can be increased.
When the liquid return pipe opening / closing valve is opened by a command from the control unit, the expansion valve and the evaporator are communicated with the liquid phase part of the gas-liquid separator through the liquid return pipe, and the liquid refrigerant in the liquid phase is communicated. Is led to the evaporator. In the gas-liquid separator, the low boiling point refrigerant evaporates and is separated from the liquid phase part, so the high boiling point refrigerant is present in the liquid refrigerant in a higher proportion than when the non-azeotropic mixed refrigerant is taken out from the take-out pipe. is doing. As a result, the proportion of the high boiling point refrigerant in the non-azeotropic mixed refrigerant that performs the refrigeration cycle can be increased.
As described above, the refrigerant that has been gas-liquid separated by the gas-liquid separator can be returned from the gas phase part or the liquid phase part to the refrigeration cycle simply by controlling each on-off valve of each pipe 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 with a simple structure.
Examples of the low boiling point refrigerant include R32, and examples of the high boiling point refrigerant include R1234yf and R1234ze (E).

  Further, in the refrigerating apparatus of the present invention, the control unit, during heating operation, when the outside air temperature is lower than a predetermined value or the temperature of the evaporator is lower than a predetermined value, opens the extraction pipe opening / closing valve, The on-off valve for the gas return pipe is opened, and a separation operation for returning the gas refrigerant separated by the gas-liquid separator from the gas return pipe to the evaporator side is performed.

During heating operation, the temperature of the evaporator is low because the outside air temperature is generally low. If the temperature of the evaporator falls below a predetermined value, a problem such as frost formation on the evaporator occurs. Therefore, when the outside air temperature is less than the specified value or the evaporator temperature is less than the specified value, the gas return pipe opening / closing valve is opened to separate the gas refrigerant separated by the gas-liquid separator (mainly low boiling point). (Refrigerant) is returned to the evaporator side via the gas return pipe to increase the proportion of low boiling point refrigerant in the refrigeration cycle. At this time, the non-azeotropic mixed refrigerant from the refrigeration cycle is led to the gas-liquid separator from the refrigeration cycle by opening the on-off valve for the extraction pipe, and the gas-liquid separator performs gas-liquid separation to lower the boiling point. By returning the refrigerant to the refrigeration cycle, further increase in the proportion of the low boiling point refrigerant in the refrigeration cycle is promoted.
By performing such a separation operation, the high-boiling-point refrigerant is separated from the non-azeotropic mixed refrigerant performing 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 in, and to suppress, for example, frost formation.
As the predetermined value of the outside air temperature and the predetermined value of the temperature of the evaporator, for example, a temperature at which the temperature of the evaporator is lowered and frost may occur is selected.

  Further, in the refrigerating apparatus of the present invention, the control unit, after a predetermined period of time has elapsed after starting the separation operation, or after the superheat degree of the non-azeotropic mixed refrigerant sucked by the compressor becomes less than a predetermined value. The opening / closing valve for the extraction pipe is closed.

After a predetermined period of time has passed since the start of the separation operation, or after the superheat degree of the non-azeotropic mixed refrigerant sucked by the compressor becomes less than a predetermined value, the on-off valve for the take-out pipe is closed, thereby the refrigeration cycle. The removal of a part of the non-azeotropic mixed refrigerant to the gas-liquid separator is stopped. Thereby, the control for increasing the proportion of the low boiling point refrigerant in the non-azeotropic mixed refrigerant performing the refrigeration cycle is stopped, and the operation can be continued with the composition of the non-azeotropic mixed refrigerant after the separation operation. ..
The "predetermined period" after a predetermined period has elapsed from 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.
The "predetermined value", which is the degree of superheat of the refrigerant sucked by the compressor less than the predetermined value, is a value set to avoid liquid compression of the compressor, for example.

  Further, in the refrigerating apparatus of the present invention, the control unit opens the extraction pipe opening / closing valve when the outside air temperature is equal to or higher than a predetermined value or the discharge gas temperature discharged from the compressor is equal to or higher than a predetermined value. The gas return pipe on-off valve is closed, and the liquid return pipe on-off valve is opened.

When the outside air temperature is equal to or higher than the predetermined value, there is no possibility of trouble such as frost formation on the evaporator. Therefore, when the outside air temperature becomes equal to or higher than the predetermined value, the on-off valve for the gas return pipe is closed to stop the low boiling point refrigerant from being preferentially returned to the refrigeration cycle. Then, the on-off valve for the liquid return pipe is opened to return the high-boiling-point refrigerant present in the liquid phase portion into the refrigeration cycle. At this time, the on-off valve for the take-out pipe is also opened to guide the non-azeotropic mixed refrigerant from the refrigeration cycle to the gas-liquid separator, and the gas-liquid separator performs gas-liquid separation to increase the temperature in the liquid phase. By preferentially returning the boiling point refrigerant into the refrigeration cycle, the increase in the proportion of the high boiling point refrigerant in the refrigeration cycle is promoted.
In this way, by performing the mixing operation of mixing the high boiling point refrigerant in the non-azeotropic mixed refrigerant performing the refrigeration cycle, the proportion of the high boiling point refrigerant in the non-azeotropic mixed refrigerant is increased, and the mixing at the time of refrigerant charging is performed. Can be returned to proportions.
In addition, 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 charging the refrigerant by the mixing operation.

  Further, in the refrigerating apparatus of the present invention, the control unit opens the extraction pipe opening / closing valve and the gas return pipe opening / closing valve during a 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, during the cooling operation, a separation operation in which the on-off valve for the extraction pipe and the on-off valve for the gas return pipe are opened is performed to increase the proportion of the low boiling point refrigerant in the non-azeotropic mixed refrigerant that performs the refrigeration cycle. As a result, highly efficient cooling operation can be realized.

  Further, in the refrigeration apparatus of the present invention, the control unit opens the extraction pipe opening / closing valve and opens / closes the gas return pipe when the temperature of the discharge gas discharged from the compressor is equal to or higher than a predetermined value. The valve is closed, and the on-off valve for the liquid return pipe is opened.

  When the proportion of the low boiling point refrigerant in the non-azeotropic mixed refrigerant that performs the refrigeration cycle increases, the discharge gas temperature of the compressor may increase excessively. Therefore, if the discharge gas temperature exceeds a specified value, perform the mixed operation by opening the outlet pipe on-off valve, closing the gas return pipe on-off valve, and opening the liquid return pipe on-off valve. Then, the ratio of the high boiling point refrigerant in the non-azeotropic mixed refrigerant is increased to return to the mixing ratio when the refrigerant is filled. As a result, it is possible to protect the equipment by avoiding the discharge gas temperature of the compressor from becoming excessively high.

Further, the control method of the refrigerating apparatus of the present invention, a compressor for compressing a non-azeotropic mixed refrigerant in which a low boiling point refrigerant and a high boiling point refrigerant having different boiling points are mixed, and a non-azeotropic mixture guided from the compressor. A condenser for condensing the refrigerant, 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, and the condenser An extraction pipe for taking out a part of the non-azeotropic mixed refrigerant from between the expansion valve, an opening / closing valve for an extraction pipe provided in the extraction pipe, and a pipe connected to the extraction pipe to store the non-azeotropic mixed refrigerant. A non-azeotropic mixture separated by the gas-liquid separator by connecting the gas-liquid separator for separating the gas-liquid with the expansion valve and the evaporator and the gas phase part in the gas- liquid separator. a gas return pipe returning the gas refrigerant into between the gas phase of the refrigerant and the expansion valve and the evaporator, said A gas return pipe opening / closing valve provided in the return pipe, a liquid return pipe connecting between the expansion valve and the evaporator and a liquid phase portion in the gas-liquid separator, and the liquid return pipe. A method for controlling a refrigerating apparatus including an on-off valve for a liquid return pipe provided, which comprises performing on-off control of the on-off valve for an extraction pipe, the on-off valve for a gas return pipe, and the on-off valve for a liquid return pipe. Is characterized by.

By simply controlling each on-off valve of each pipe connected to the gas-liquid separator, the refrigerant that has been gas-liquid separated by the gas-liquid separator can be returned from the gas phase part or the liquid phase part to the refrigeration cycle. With such a configuration, the mixing ratio of the non-azeotropic mixed refrigerant can be arbitrarily changed.
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 ratio of the low boiling point refrigerant, by raising the saturation temperature in the evaporator, the frost formation on the evaporator is prevented. Can be suppressed.
During the cooling operation, by performing a separation operation in which the on-off valve for the extraction pipe and the on-off valve for the gas return pipe are opened, the proportion of the low boiling point refrigerant in the non-azeotropic mixed refrigerant that performs the refrigeration cycle is increased, Efficient cooling operation can be realized.

It is a refrigerant circuit of the refrigerating device concerning one embodiment of the present invention, and is a schematic structure figure showing normal operation (filling 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 mixed operation at the time of heating operation. It is a flow chart showing control at the time of heating operation. It is a schematic block diagram of the refrigerant circuit which showed the normal operation (filling composition) at the time of cooling operation. It is a schematic block diagram of the refrigerant circuit which showed the separation operation at the time of cooling operation. It is a schematic block diagram of the refrigerant circuit which showed the normal operation (separation composition) at the time of cooling operation. It is a schematic block diagram of the refrigerant circuit which showed the mixing operation at the time of cooling operation. It is the flowchart which showed the control at the time of cooling operation. It is the p (pressure) -h (enthalpy) diagram which showed the temperature slip of a non-azeotropic mixed refrigerant. The temperature slip according to the mixing ratio of the non-azeotropic mixed refrigerant is shown, (a) is the temperature slip at the saturation temperature of 40 ° C, and (b) is the temperature slip at the saturation temperature of 10 ° C. It is the graph which showed the change of COP according to the mixing ratio of a non-azeotropic mixed refrigerant.

An embodiment according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a refrigerant circuit configuration of the refrigeration system 1 of this embodiment. The refrigeration system 1 is used as, for example, 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 refrigeration apparatus 1 uses a non-azeotropic mixed refrigerant in which R32 and R1234ze (E) are mixed as the refrigerant. R32 is a low boiling point refrigerant having a lower boiling point than that of R1234ze (E). R1234ze (E) is a high boiling point refrigerant having a higher boiling point than R32. Note that R1234yf may be used instead of R1234ze (E).

  The refrigeration system 1 includes a compressor 3 that compresses a non-azeotropic mixed refrigerant (hereinafter, also 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 for performing a refrigeration cycle is configured.

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

The condenser 5 is an indoor heat exchanger, and warms the indoor air to perform heat exchange during the heating operation, thereby condensing the high-pressure gas refrigerant guided 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 heat-exchanges with the outside air as an outdoor heat exchanger during heating operation to evaporate the refrigerant expanded by the expansion valve 7. .. At the refrigerant outlet of the evaporator 9, an evaporator outlet temperature sensor 15 that measures the temperature of the evaporated refrigerant is provided. The output of the evaporator outlet temperature sensor 15 is transmitted 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 the outdoor unit that houses the compressor 3 and the evaporator 9.

  An extraction pipe 19 is provided between the extraction position A between the condenser 5 and the expansion valve 7 and the upper portion of the gas-liquid separator 17. An outlet pipe opening / closing valve 20 is provided in the outlet pipe 19. The extraction pipe opening / closing valve 20 is, for example, an electromagnetic valve, and is opened / closed by a command from the control unit.

  A gas return pipe 21 is provided between the gas-liquid separator 17 and the confluent position B between the expansion valve 7 and the evaporator 9. The upstream end 21 a of the gas return pipe 21 is located above the gas-liquid separator 17 and opens at the gas phase portion of the refrigerant separated in the gas-liquid separator 17. The gas return pipe 21 is provided with an on-off valve 22 for gas return pipe. The gas return pipe opening / closing valve 22 is, for example, an electromagnetic valve, and is opened / closed by a command from the control unit.

  A liquid return pipe 23 is provided between the joining position B between the expansion valve 7 and the evaporator 9 and the gas-liquid separator 17. The upstream end 23a of the liquid return pipe 23 is located at the lower portion (or bottom portion) of the gas-liquid separator 17 and opens at 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 opening / closing valve 24. The liquid return pipe opening / closing valve 24 is, for example, an electromagnetic valve, and is opened / closed by a command from the control unit.

  The control unit includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is installed in a ROM or other storage medium in advance, provided in a state of being stored in a computer-readable storage medium, or delivered via 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.

<During heating operation>
Next, the operation mode during the heating operation of the refrigeration system 1 having the above configuration will be described.
[Normal operation (filled composition): During heating operation]
FIG. 1 shows the normal operation (encapsulated composition) during the heating operation. In this normal operation, the non-azeotropic mixed refrigerant is operated with a composition having the same mixing ratio (for example, R32: R1234ze (E) = 1: 1 mixing ratio) as when the refrigeration system 1 is enclosed. ..

  The outlet pipe opening / closing valve 20 is closed, the gas return pipe opening / closing valve 22 is opened, and the liquid return pipe opening / closing valve 24 is opened. In each figure, open valves are shown in white and closed valves are shown in black.

By closing the opening / closing valve 20 for the extraction pipe, the refrigerant is not taken out from the refrigeration cycle, and the mixing ratio of the refrigerant for the refrigeration cycle is not changed. Further, by opening the liquid return pipe on-off valve 24, the liquid refrigerant is not stored in the gas-liquid separator 17, and the mixing ratio of the refrigerant for the refrigeration cycle is not changed.
The gas return pipe opening / closing valve 22 is opened to equalize the refrigerant pressure after being expanded by the expansion valve 7. This makes it possible to prevent the low-boiling-point refrigerant from remaining unevaporated during normal operation, and preventing a liquid-sealed state in which the gas-liquid separator 17 is filled with unevaporated refrigerant during stoppage. This is because.

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

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

  By opening the extraction pipe opening / closing valve 20, a part of the 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, the gas return pipe on-off valve 22 is opened, and the pressure between the expansion valve 7 and the evaporator 9 is set to a low pressure. R32, which is a low-boiling-point refrigerant introduced into the above, is preferentially evaporated over R1234ze (E), which is a high-boiling-point refrigerant. Then, R32 evaporated in the gas-liquid separator 17 passes through the gas return pipe 21 and is returned from the confluence position B to the evaporator 9 to be used as a refrigerant for performing a refrigeration cycle. As a result, the mixing ratio of R32 in the refrigerant performing the refrigeration cycle increases.

[Normal operation (separated composition): During heating operation]
FIG. 3 shows the normal operation (separated composition) during the heating operation. This normal operation is performed after the above-described separation operation, and is operated in a state in which R1234ze (E) in the refrigerant that performs the refrigeration cycle is separated and the mixing ratio of R32 is high. Is.

  The outlet pipe opening / closing valve 20 is closed, the gas return pipe opening / closing valve 22 is opened, and the liquid return pipe opening / closing valve 24 is closed.

By closing the opening / closing valve 20 for the extraction pipe, the refrigerant is not taken out from the refrigeration cycle, and the mixing ratio of the refrigerant for the refrigeration cycle is not changed. Further, by closing the liquid return pipe 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 on-off valve 22 for the gas return pipe is opened to guide the R32 separated in the gas-liquid separator 17 to the evaporator 9 via the gas return pipe 21.

[Mixed operation: During heating operation]
FIG. 4 shows the mixed operation during the heating operation. The mixing operation is performed after the above-described normal operation (separation composition), and is an operation in which R1234ze (E) is mixed with the refrigerant that performs the refrigeration cycle to reduce the mixing ratio of R32 in the refrigerant.

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

  The liquid refrigerant is introduced into the gas-liquid separator 17 from between the condenser 5 and the expansion valve 7 by opening the extraction pipe opening / closing valve 20. Since the gas return pipe on-off valve 22 is closed in the gas-liquid separator 17, R32 evaporated in the gas-liquid separator 17 is not supplied from the merging position B to the refrigerant for the refrigeration cycle. .. On the other hand, since the liquid return pipe opening / closing valve 24 is opened, the liquid refrigerant stored in the gas-liquid separator 17 is guided to the evaporator 9 from the confluence position B through the liquid return pipe 23. As a result, the liquid refrigerant in the gas-liquid separator 17 in which R1234ze (E) has been concentrated by the separation operation (see FIG. 2) is returned to the refrigerant for the refrigeration cycle, so that R1234ze (E for the refrigerant for the refrigeration cycle is used. ) Mixing ratio increases.

  Next, a method of controlling the refrigeration system 1 during heating operation will be described with reference to FIG. Each step shown below is performed by a command from the control unit.

  When the operation is started, it is determined whether the outside air temperature is lower 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 lower 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. As a result, the temperature slip in the evaporator 9 becomes small (see FIG. 12B), the low pressure in the evaporator 9 rises, and frost formation is prevented.

  When it is determined in step S1 that the outside air temperature is 10 ° C. or higher, the process proceeds to step S3, and normal operation (filled composition) is performed (see FIG. 1). In the normal operation (filling composition), the mixing ratio in the refrigerant performing the refrigeration cycle is equal to that in the refrigerant charging, 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 kept 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) during the normal operation (filling composition) in step S3 (step S4), the unit is stopped. Whether or not there is a command is determined (step S5). When the unit stop command is issued, the refrigerating apparatus 1 is stopped and the process ends. When the unit stop command is not issued, the process returns to step S3 to continue the normal operation (filling composition).
When the temperature Tho-R measured by the evaporator outlet temperature sensor 15 becomes less than -3 ° C in step S4, the process proceeds to step S3 and the separation operation is performed. Due to the separation operation, the low pressure of the evaporator 9 rises and frost formation is prevented.

  During the separation operation in step S2, it is determined whether the suction superheat degree of the compressor 3 is lower than 2 ° C. or whether a predetermined time (for example, 1 hour) has elapsed after 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, if the intake 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 intake 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 (separated composition), R1234ze (E) is separated from the refrigerant in which the refrigeration cycle is performed, and the operation in which the mixing ratio of R32 is increased is performed. As a result, frost formation on the evaporator 9 is suppressed, and operation with a high COP is performed as shown in FIG.

  During 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). When the discharge temperature Tho-D exceeds 110 ° C., the process proceeds to step S9 and the mixing operation (see FIG. 4) is performed. In the mixed operation, R1234ze (E) is mixed in the refrigerant that performs the refrigeration cycle, and the refrigerant is operated so as to approach the mixing ratio at the time of enclosing. As a result, the mixing ratio of R32 in the refrigerant performing the refrigeration cycle becomes small, and the discharge temperature drops. The mixing operation is terminated after a predetermined time (for example, 5 minutes) has elapsed, and the process proceeds to step S3 to perform the normal operation (encapsulated composition).

  When the discharge temperature Tho-D does not exceed 110 ° C. in step S8, the process proceeds to step S10, and it is determined whether or not there is a unit stop command. When the unit stop command is not issued, the process returns to step S7 and the normal operation (separation composition) is continued. When the unit stop command is issued, the process proceeds to step S11, and after the mixing operation is performed for a predetermined time (for example, 5 minutes), the refrigerating apparatus 1 is stopped and the process ends. By performing the mixing operation before stopping the refrigerating apparatus 1, the mixing ratio in the refrigerant that performs the refrigerating cycle at the next startup is returned when the refrigerant is charged.

<During cooling operation>
Next, an operation mode during the cooling operation of the refrigerating apparatus 1 having the above configuration will be described. The cooling operation is switched from the heating operation by switching a four-way valve (not shown) provided on the discharge side of the compressor 3. As a result, the condenser during heating operation switches to the evaporator (indoor heat exchanger) during cooling operation, and the evaporator during heating operation switches to the condenser (outdoor heat exchanger) during cooling operation.

[Normal operation (filled composition): During cooling operation]
FIG. 6 shows the normal operation (encapsulated composition) during the cooling operation. In this normal operation, the non-azeotropic mixed refrigerant is operated with a composition having the same mixing ratio (for example, R32: R1234ze (E) = 1: 1 mixing ratio) as when the refrigeration system 1 is enclosed. ..

  The outlet pipe opening / closing valve 20 is closed, the gas return pipe opening / closing valve 22 is opened, and the liquid return pipe opening / closing valve 24 is closed.

By closing the opening / closing valve 20 for the extraction pipe, the refrigerant is not taken out from the refrigeration cycle, and the mixing ratio of the refrigerant for the refrigeration cycle is not changed. In addition, by opening the liquid return pipe on-off valve 24, the liquid refrigerant is not accumulated in the gas-liquid separator 17, and the mixing ratio of the refrigerant forming the refrigeration cycle is not changed.
The gas return pipe opening / closing valve 22 is opened to equalize the refrigerant pressure after being expanded by the expansion valve 7. This makes it possible to prevent the low boiling point refrigerant from remaining unevaporated during normal operation, and to prevent a liquid-sealed state in which the gas-liquid separator is filled with unevaporated refrigerant during stoppage. Is.

[Separation operation (during cooling operation)]
FIG. 7 shows the separation operation during the cooling operation. The separation operation is performed after the normal operation (encapsulated composition) described above, and R1234ze (E) (high boiling point refrigerant) is separated from the refrigerant that performs the refrigeration cycle, and R32 (low temperature) in the refrigerant that performs the refrigeration cycle is separated. This is an operation in which the mixing ratio of the boiling point refrigerant) is increased.

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

  The liquid refrigerant is introduced into the gas-liquid separator 17 from between the condenser 5 and the expansion valve 7 by opening the extraction pipe opening / closing valve 20. In the gas-liquid separator 17, the gas return pipe on-off valve 22 is opened, and the pressure between the expansion valve 7 and the evaporator 9 is set to a low pressure. R32, which is a low-boiling-point refrigerant introduced into the above, is preferentially evaporated over R1234ze (E), which is a high-boiling-point refrigerant. Then, R32 evaporated in the gas-liquid separator 17 passes through the gas return pipe 22 and is returned from the confluence position B to the evaporator 9, and is used as a refrigerant for performing a refrigeration cycle. As a result, the mixing ratio of R32 in the refrigerant performing the refrigeration cycle increases.

[Normal operation (separated composition): During cooling operation]
FIG. 8 shows the normal operation (separated composition) during the cooling operation. This normal operation is performed after the above-described separation operation, and is operated in a state in which R1234ze (E) in the refrigerant that performs the refrigeration cycle is separated and the mixing ratio of R32 is high. Is.

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

  By closing the opening / closing valve 20 for the extraction pipe, the refrigerant is not taken out from the refrigeration cycle, and the mixing ratio of the refrigerant for the refrigeration cycle is not changed. Further, by closing the liquid return pipe 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 on-off valve 22 for the gas return pipe is closed unlike the normal operation (separation composition) during the heating operation shown in FIG. This is because the outside air temperature during the cooling operation is higher than that during the heating operation, so the environmental temperature inside 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 and gas. This is because there is a risk that the refrigerant may pass through the return pipe 21 and join the refrigerant for the refrigeration cycle. In addition, when the gas-liquid separator 17 is installed in an environment (for example, indoors) that is less affected by the outside air temperature than in the outdoor unit, the gas return pipe for the gas return pipe is similar to the normal operation during heating operation (separation composition). The on-off valve 22 may be opened.

[Mixed operation: cooling operation]
FIG. 9 shows the mixed operation during the cooling operation. The mixing operation is performed after the above-described normal operation (separation composition), and is an operation in which R1234ze (E) is mixed with the refrigerant that performs the refrigeration cycle to reduce the mixing ratio of R32 in the refrigerant.

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

  The liquid refrigerant is introduced into the gas-liquid separator 17 from between the condenser 5 and the expansion valve 7 by opening the extraction pipe opening / closing valve 20. Since the gas return pipe on-off valve 22 is closed in the gas-liquid separator 17, R32 evaporated in the gas-liquid separator 17 is not supplied from the merging position B to the refrigerant for the refrigeration cycle. .. On the other hand, since the liquid return pipe opening / closing valve 24 is opened, the liquid refrigerant stored in the gas-liquid separator 17 is guided to the evaporator 9 from the confluence position B through the liquid return pipe 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 for the refrigeration cycle, so that R1234ze (E in the refrigerant for the refrigeration cycle is used. ) Mixing ratio increases.

  Next, a control method of the refrigeration system 1 during the cooling operation will be described with reference to FIG. Each step shown below is performed by a command 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. Thereby, the cooling operation with improved COP is performed (see FIG. 13).

  During the separation operation in step S21, it is determined whether the suction superheat degree of the compressor 3 is lower than 2 ° C. or whether a predetermined time (for example, 1 hour) has elapsed after the separation operation was started ( Step S22).

  In step S22, if the intake superheat is not less than 2 ° C. and one hour has not elapsed from the separation operation, the process returns to step S21 and the separation operation is continued.

  In step S22, when the intake superheat becomes less than 2 ° C. or when one hour or more has passed 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 (separated composition), R1234ze (E) is separated from the refrigerant in which the refrigeration cycle is performed, and operation in which the mixing ratio of R32 is increased is performed. As a result, the cooling operation with a high COP is continued.

  It is determined whether or not the discharge temperature Tho-D measured by the discharge temperature sensor 13 exceeds a predetermined value (for example, 110 ° C.) during the normal operation (separation composition) in step S23 (step S24). When the discharge temperature Tho-D exceeds 110 ° C., the process proceeds to step S25 and the mixing operation (see FIG. 9) is performed. In the mixed operation, R1234ze (E) is mixed in the refrigerant that performs the refrigeration cycle, and the refrigerant is operated so as to approach the mixing ratio at the time of enclosing. As a result, the mixing ratio of R32 in the refrigerant performing the refrigeration cycle becomes small, and the discharge temperature drops. The mixing operation ends after a predetermined time (for example, 5 minutes) has elapsed, and the process proceeds to step S26 to perform the normal operation (encapsulated composition) (see FIG. 6).

  In the normal operation (filling composition), the mixing ratio in the refrigerant performing the refrigeration cycle is equal to that in the 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 a predetermined value. The operation will be kept below the value.

  It is determined whether or not there is a unit stop command during the normal operation (filling composition) in step S26 (step S27). When the unit stop command is issued, the refrigerating apparatus 1 is stopped and the process ends. If the unit stop command is not issued, the process returns to step S26 to continue the normal operation (encapsulated composition).

  When the discharge temperature Tho-D does not exceed 110 ° C. in step S24, the process proceeds to step S28, and it is determined whether or not there is a unit stop command. When the unit stop command is not issued, the process returns to step S23 to continue the normal operation (separation composition). When the unit stop command is issued, the process proceeds to step S29, the mixing operation is performed for a predetermined time (for example, 5 minutes), and then the refrigerating apparatus 1 is stopped and the process ends. By performing the mixing operation before stopping the refrigerating apparatus 1, the mixing ratio in the refrigerant that performs the refrigerating cycle at the next startup is returned when the refrigerant is charged.

As described above, according to this embodiment, the following operational effects are exhibited.
By simply connecting the pipes 19, 21, 23 to the gas-liquid separator 17 and controlling the on-off valves 20, 22, 24, the gas refrigerant or the liquid refrigerant separated by the gas-liquid separator 17 can be used in a refrigeration cycle. 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 with a simple structure.

  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 becomes equal to or lower than a predetermined value, a problem such as frost formation on the evaporator occurs. 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 pipe on-off valve 22 is opened to freeze the gas. Increase the proportion of R32 (low boiling point refrigerant) in the cycle. At this time, by opening the extraction pipe opening / closing valve 20 as well, the refrigerant is guided from the refrigeration cycle to the gas-liquid separator 17, and the gas-liquid separator 17 performs gas-liquid separation to put R32 into the refrigeration cycle. By returning, the rate increase of R32 in the refrigeration cycle is further promoted. By performing such a separation operation (see FIG. 2), R1234ze (E) (high-boiling-point refrigerant) is separated from the refrigerant that performs the refrigeration cycle, and a separation operation that increases the ratio of R32 is performed, thereby eliminating the temperature slip. It can be made smaller and the saturation temperature in the evaporator 9 can be raised to suppress frost formation.

  The extraction pipe opening / closing valve 20 is closed after a predetermined period (for example, 1 hour) has elapsed after the separation operation (see FIG. 2) or after the intake superheat becomes less than a predetermined value (for example, 2 ° C.). As a result, the extraction of part of the refrigerant for the refrigeration cycle to the gas-liquid separator 17 is stopped (see FIG. 3). This makes it possible to stop the control for increasing the ratio of R32 in the refrigerant that performs the refrigeration cycle and perform the normal operation (separation composition) 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 problem 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 pipe on-off valve 22 is closed to stop the R32 from being returned preferentially during the refrigeration cycle. Then, the on-off valve 24 for the liquid return pipe is opened to return the R1234ze (E), which is mostly present in the liquid refrigerant in the gas-liquid separator 17, to the refrigeration cycle. At this time, by opening the extraction pipe opening / closing valve 20 as well, the refrigerant is guided from the refrigeration cycle to the gas-liquid separator 17, and the gas-liquid separator 17 performs gas-liquid separation to R1234ze (in the liquid phase). By preferentially returning E) into the refrigeration cycle, an increase in the proportion of R1234ze (E) in the refrigeration cycle is promoted.
In this way, by performing the mixing operation of mixing R1234ze (E) in the refrigerant that performs the refrigeration cycle, the ratio of R1234ze (E) in the refrigerant can be increased and returned to the mixing ratio at the time of charging the refrigerant. ..
Further, when the temperature of the discharge gas discharged from the compressor 3 becomes equal to or higher than a predetermined value (for example, 110 ° C.), the discharge gas temperature is lowered by returning the mixing ratio of the refrigerant by the mixing operation when the refrigerant is charged. You can

  During the cooling operation, the separation operation (see FIG. 7) in which the extraction pipe opening / closing valve 20 and the gas return pipe opening / closing valve 22 are opened is performed to increase the proportion of R32 in the refrigerant in the refrigeration cycle. As a result, highly efficient cooling operation can be realized.

  Even during the cooling operation, when the discharge gas temperature becomes equal to or higher than a predetermined value (for example, 110 ° C.), the extraction pipe opening / closing valve 20 is opened, the gas return pipe opening / closing valve 22 is closed, and the liquid return pipe is opened. By performing the mixing operation in which the opening / closing valve 24 is opened (see FIG. 9), the ratio of R1234ze (E) in the refrigerant is increased to return to the mixing ratio at the time of charging the refrigerant. As a result, it is possible to protect the equipment by avoiding the discharge gas temperature of the compressor 3 from becoming excessively high.

  In addition, in the above-described embodiment, the refrigerating 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 refrigerating apparatus that performs only heating operation or only cooling operation. be able to.

1 Refrigeration Device 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 Pipe 20 Extraction Pipe Open / Close Valve 21 Gas Return Pipe 22 Gas Return Open / close valve for piping 23 Liquid return piping 24 Open / close valve for liquid return piping A Extraction position B Merging position

Claims (7)

A compressor for compressing a non-azeotropic mixed refrigerant in which a low boiling point refrigerant and a high boiling point refrigerant 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 mixed refrigerant from between the condenser and the expansion valve,
An on-off valve for extraction pipe provided in the extraction pipe,
A gas-liquid separator that is connected to the extraction pipe and stores the non-azeotropic mixed refrigerant into gas and liquid.
The gas phase of the non-azeotropic mixed refrigerant separated by the gas-liquid separator is connected between the expansion valve and the evaporator and the gas phase part in the gas- liquid separator, and the expansion valve and the evaporation A gas return pipe that returns as a gas refrigerant to and from the vessel ,
An on-off valve for gas return pipe provided in the gas return pipe,
A liquid return pipe connecting between the expansion valve and the evaporator and a liquid phase portion in the gas-liquid separator,
On-off valve for liquid return pipe provided in the liquid return pipe,
A control unit for controlling the on-off valve for the extraction pipe, the on-off valve for the gas return pipe and the on-off valve for the liquid return pipe,
A refrigerating apparatus comprising:   During heating operation, the control unit opens the outlet pipe opening / closing valve and opens the gas return pipe opening / closing valve when the outside air temperature is lower than a predetermined value or the evaporator temperature is lower than a predetermined value. The refrigerating apparatus according to claim 1, wherein the gas refrigerant separated by the gas-liquid separator is separated from the gas return pipe to the evaporator side.   The control unit closes the extraction pipe opening / closing valve after a predetermined period of time has elapsed from 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 refrigerating apparatus according to claim 2, wherein   When the outside air temperature is equal to or higher than a predetermined value or the discharge gas temperature discharged from the compressor is equal to or higher than a predetermined value, the control unit opens the extraction pipe opening / closing valve to open the gas return pipe opening / closing valve. The refrigeration apparatus according to claim 2, wherein the refrigeration apparatus is closed and the liquid return pipe opening / closing valve is opened.   The refrigeration apparatus according to claim 1, wherein the control unit opens the on-off valve for the extraction pipe and opens the on-off valve for the gas return pipe during a cooling operation.   When the temperature of the discharge gas discharged from the compressor is equal to or higher than a predetermined value, the control unit opens the opening / closing valve for the extraction pipe and closes the opening / closing valve for the gas return pipe, and the liquid return pipe. The refrigerating apparatus according to claim 4, wherein the on-off valve for the vehicle is opened. A compressor for compressing a non-azeotropic mixed refrigerant in which a low boiling point refrigerant and a high boiling point refrigerant 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 mixed refrigerant from between the condenser and the expansion valve,
An on-off valve for extraction pipe provided in the extraction pipe,
A gas-liquid separator that is connected to the extraction pipe and stores the non-azeotropic mixed refrigerant into gas and liquid.
By connecting the expansion valve and the evaporator and the gas phase part in the gas-liquid separator, the gas phase of the non-azeotropic mixed refrigerant separated by the gas-liquid separator is evaporated by the expansion valve and the evaporator. A gas return pipe that returns as a gas refrigerant to and from the vessel ,
An on-off valve for gas return pipe provided in the gas return pipe,
A liquid return pipe connecting between the expansion valve and the evaporator and a liquid phase portion in the gas-liquid separator,
On-off valve for liquid return pipe provided in the liquid return pipe,
A method for controlling a refrigerating apparatus comprising:
A method for controlling a refrigerating apparatus, which controls opening / closing of the extraction pipe opening / closing valve, the gas return piping opening / closing valve, and the liquid return piping opening / closing valve.

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