JP5982017B2 - Dual refrigeration cycle equipment - Google Patents

Description

  Embodiments of the present invention relate to a dual refrigeration cycle apparatus including a high temperature side refrigeration cycle and a low temperature side refrigeration cycle.

  A conventionally known binary refrigeration cycle apparatus includes a high temperature side refrigeration cycle and a low temperature side refrigeration cycle, and the high temperature side refrigeration cycle and the low temperature side refrigeration cycle share one cascade heat exchanger (intermediate heat exchanger), The refrigerant circulating in the high temperature side refrigeration cycle and the refrigerant circulating in the low temperature side refrigeration cycle are heat-exchanged by a cascade heat exchanger, and water or hot water is heated by the high temperature side refrigerant circulating in the high temperature side refrigeration cycle. Is generated.

In general, when the refrigeration cycle is started when the outside air temperature is low, the temperature of the refrigeration oil in the compressor constituting the refrigeration cycle decreases. Therefore, as the pressure increases due to the start of the compressor, the refrigerant is dissolved in the refrigerating machine oil, and the refrigerating machine oil is diluted. As the dilution of the refrigerating machine oil proceeds, the amount of the refrigerating machine oil discharged to the outside of the compressor together with the refrigerant increases, the oil level in the compressor decreases, and the lubrication of the compression mechanism part tends to be insufficient.
In particular, in the high-temperature side refrigeration cycle of the dual refrigeration cycle apparatus that generates high-temperature water, the condensation pressure rises quickly and the condensation pressure is high, so that dilution of the refrigeration oil is easily promoted and the amount of oil discharged from the refrigeration oil increases. There is a problem.

International Publication WO2012 / 128229 A1

  In view of the above-described prior art, an object of the present invention is to provide a dual refrigeration cycle apparatus capable of suppressing the amount of refrigerating machine oil discharged outside the compressor during startup at a low outside air temperature. .

A binary refrigeration cycle apparatus according to an embodiment of the present invention provided to solve the above problems includes a high temperature side compressor, a high temperature side condenser, a high temperature side expansion device, a cascade heat exchanger, and a high temperature side accumulator. A high temperature side refrigeration circuit that communicates via a pipe, a low temperature side compressor, a cascade heat exchanger, a low temperature side expansion device, a low temperature side evaporator, and a low temperature side accumulator that communicates via a low temperature side refrigerant pipe A high temperature side bypass circuit connecting the discharge side of the high temperature side compressor and the inlet side of the high temperature side accumulator, a high temperature side bypass valve provided in the high temperature side bypass circuit, and a discharge of the low temperature side compressor and the low temperature-side bypass circuit for communicating the inlet side of the the side cold accumulator, and the low temperature side bypass valve provided in the low temperature side bypass circuit, at startup, the outside air temperature is first For temperatures below, the open-out the hot side bypass valve, when the outside air temperature is below a lower second temperature than the first temperature, further comprising: a Open control means the low temperature side bypass valve It is characterized by that.
It is desirable that the binary refrigeration cycle apparatus having the above features further has the following preferred embodiments.
Further, it is desirable that the control means drives the high temperature side compressor at a predetermined operation frequency lower than an operation frequency during normal operation while the high temperature side bypass valve is open.
The control unit includes a low outside air temperature startup mode selecting means for determining whether or not to perform a low-outside air temperature startup mode based on the inlet side of the temperature and the outside air temperature of the heated fluid in the high temperature side condenser The bypass circuit opening time setting means for setting the time to open the bypass circuit according to the outside air temperature when the low outside temperature start mode is executed, and the high temperature that opens the high temperature side bypass circuit according to the outside temperature when the low outside temperature start mode is executed Side bypass control means and low temperature side bypass control means for opening the low temperature side bypass circuit in addition to the high temperature side bypass circuit according to the outside air temperature when the low outside air temperature activation mode is executed.
The dual refrigeration cycle apparatus according to the present invention is not limited to the above-described embodiment unless the spirit of the present invention is changed according to the application destination.

According to the above-described embodiment of the present invention, it is possible to provide a dual refrigeration cycle apparatus capable of suppressing the amount of refrigerating machine oil discharged outside the compressor during startup at a low outside air temperature.
Furthermore, the binary refrigeration cycle apparatus in the present embodiment starts the operation of the high temperature side compressor with the high temperature side bypass circuit opened when the outside air temperature is low and the dilution of the refrigeration oil is likely to occur. It is possible to raise the temperature of the refrigerating machine oil in the compressor by flowing a high-temperature gas refrigerant into the interior. Accordingly, it is possible to suppress the refrigerant from being dissolved in the refrigerating machine oil, and to suppress the discharge amount of the refrigerating machine oil to the outside of the compressor due to dilution.
Further advantages and advantages of the embodiments of the present invention will become more apparent from the following description made with reference to the accompanying drawings.

It is a block diagram of the refrigerating cycle which shows the structure of the binary refrigerating-cycle apparatus concerning embodiment of this invention. It is a block diagram which shows the structure of the control part (controller) of the binary refrigerating-cycle apparatus concerning embodiment of this invention. It is a flowchart which shows the flow of operation | movement at the time of starting of the binary refrigerating-cycle apparatus concerning embodiment of this invention. It is explanatory drawing (table | table | tablet) which shows the relationship between the external temperature and operation | movement of the low external temperature starting mode of the binary refrigerating cycle apparatus concerning embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a configuration diagram of a refrigeration cycle showing a configuration of a binary refrigeration cycle apparatus according to an embodiment of the present invention. The dual refrigeration cycle apparatus R used as the high temperature water generating apparatus includes a high temperature side refrigeration cycle Ra, a low temperature side refrigeration cycle Rb, and a control unit 20 mounted in the housing K.

The high temperature side refrigeration cycle Ra includes a high temperature side compressor 1 that compresses the refrigerant, a hot water heat exchanger 2 (high temperature side condenser) that condenses the refrigerant, a high temperature side expansion device 3 that decompresses the refrigerant, and a low temperature side refrigeration cycle. A cascade heat exchanger 4 that exchanges heat with the Rb refrigerant and a high-temperature side accumulator 5 for gas-liquid separation of the refrigerant are provided, and these are sequentially communicated via a refrigerant pipe.
The cascade heat exchanger 4 functions as an evaporator that evaporates the refrigerant flowing through the high temperature side refrigerant flow path 4a in the high temperature side refrigeration cycle Ra. In the hot water heat exchanger 2, there are provided a refrigerant side channel 2a through which the refrigerant of the high temperature side refrigeration cycle Ra and a water side channel 2b through which water to be heated flows, and the water side channel 2b is provided with hot water. It communicates with the pipe H. A water pump 18 is provided in the hot water pipe H.

  The discharge side of the high temperature side compressor 1 and the inlet side of the high temperature side accumulator 5 are communicated by a high temperature side bypass circuit 6. The high temperature side bypass circuit 6 is provided with a high temperature side bypass valve 7 which is an on-off valve.

The low temperature side refrigeration cycle Rb includes a low temperature side compressor 11 that compresses refrigerant, a four-way valve 12 that switches a flow direction of refrigerant between a heating operation and a defrosting operation, a cascade heat exchanger 4, and a low temperature side that depressurizes the refrigerant. It has an expansion device 13, an air heat exchanger (low temperature side evaporator) 14 for evaporating the refrigerant, and a low temperature side accumulator 15, and these are sequentially communicated via refrigerant piping.
The cascade heat exchanger 4 functions as a condenser that condenses the refrigerant flowing through the low temperature side refrigerant flow path 4b in the low temperature side refrigeration cycle Rb.
A blower 19 for sending air to the air heat exchanger 14 is provided at a position facing the air heat exchanger 14.

  The discharge side of the low temperature side compressor 11 and the inlet side of the low temperature side accumulator 15 are communicated by a low temperature side bypass circuit 16. The low temperature side bypass circuit 16 is provided with a low temperature side bypass valve 17 which is an on-off valve.

In the present embodiment, R134a refrigerant is used in the high temperature side refrigeration cycle Ra, and R410A refrigerant is used in the low temperature side refrigeration cycle Rb.
R134a used for the high temperature side refrigeration cycle Ra has a lower saturated gas density and saturation pressure at the same temperature than the R410A used for the low temperature side refrigeration cycle Rb, so that it can generate high temperature water. It is suitable as a refrigerant used for the high temperature side refrigeration cycle Ra of the apparatus.

  As for refrigeration oil, PVE (polyvinyl ether) is used in the high temperature side compressor 1 of the high temperature side refrigeration cycle Ra, and POE (polyol ester) is used in the low temperature side compressor 11 of the low temperature side refrigeration cycle Rb. The In addition, PVE used as the refrigerating machine oil of the high temperature side compressor 1 is suitable as a refrigerating machine oil for the high temperature side compressor because the wear of the compression mechanism portion is less than that of the POE at a high temperature. On the other hand, PVE has the property of being easily dissolved by the R134a refrigerant as compared with POE, and has the property of increasing the amount of oil discharged when the low outside air temperature is started.

In the two-stage refrigeration cycle apparatus R configured as described above, the operation of the high temperature side refrigeration cycle Ra when the high temperature side compressor 1 is driven by the control unit (control apparatus) 20 described later, and the low temperature side compressor 11. The low temperature side refrigeration cycle Rb is operated by driving the. Furthermore, when the water supply pump 18 of the hot water pipe H is driven, water flows in the water side flow path 2b of the hot water heat exchanger 2. This water is heated by the heat radiated from the high temperature side refrigerant in the refrigerant side flow path 2a and becomes high temperature water of about 90 ° C. at the maximum. This hot water is supplied from a hot water pipe H to a place where hot water is required.
The relationship between the control unit 20 and each component is shown in FIG.

  By operating the high temperature side refrigeration cycle Ra and the low temperature side refrigeration cycle Rb, heat exchange is performed in the heat exchanger 4 including the high temperature side refrigerant flow channel 4a and the low temperature side refrigerant flow channel 4b, and the high temperature side refrigeration cycle Ra is performed. The high temperature side refrigerant is warmed by the heat radiated from the low temperature side refrigerant of the low temperature side refrigeration cycle Rb. Thereby, in the high temperature side refrigerating cycle Ra, the temperature of the refrigerant sucked into the high temperature side compressor 1 is increased, and the temperature and pressure in the high temperature side compressor 1 are compared with the temperature and pressure in the low temperature side compressor 11. The amount of heat radiated from the refrigerant side flow path 2a of the hot water heat exchanger 2 increases, and high temperature water can be generated.

Next, the control part (control apparatus) of the binary refrigeration cycle apparatus R concerning embodiment of this invention is demonstrated based on the block diagram of FIG.
The two-stage refrigeration cycle apparatus R includes a control unit 20 including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like inside the housing K.
The control unit 20 includes a high temperature side compressor 1 drive control inverter circuit 21, a low temperature side compressor 11 drive control inverter circuit 22, a blower 19 drive control inverter circuit 23, a high temperature side expansion device 3, and a low temperature side expansion device. 13, the four-way valve 12, the high temperature side bypass valve 7, the low temperature side bypass valve 17, and the pump 18 are connected and their operations are controlled.

  The controller 20 includes temperature sensors 31a and 31b and pressure sensors 32a and 32b provided on the discharge side of the high temperature side compressor 1 and the low temperature side compressor 11, and temperature sensors 33a and 33b and pressure sensor 34a provided on the suction side. , 34b, an inlet water temperature sensor 35 provided on the inlet side of the water channel 2b of the hot water heat exchanger 2, an outlet water temperature sensor 36 provided on the outlet side, and a temperature sensor (not shown) provided on the cascade heat exchanger 4 ), A temperature sensor (not shown) provided in the air heat exchanger 14, and an outside air temperature sensor 37 provided in the vicinity of the air heat exchanger 14. 2 shows a state in which the temperature sensor 31a, the inlet water temperature sensor 35, and the outside air temperature sensor 37 are connected to the control unit 20.

  The high temperature side compressor 1 drive control inverter circuit 21 rectifies the voltage of a power source such as a commercial AC power source, converts it into a voltage having a frequency according to a command from the control unit 20, and compresses the high temperature side compressor 1. Output to the machine motor 1M. This output becomes the driving power for the compressor motor 1M. Similarly, the low temperature side compressor 11 drive control inverter circuit 22 drives the compressor motor 11M of the low temperature side compressor 11, and the blower 19 drive control inverter circuit 23 drives the fan motor 19M of the blower 19. The water pump 18 is also driven by a water pump drive control inverter (not shown).

  The control unit 20 determines operating conditions of each unit based on information such as operating conditions input from an operation unit (both not shown) such as a touch panel and a remote controller and detection signals from various sensors, and the compressor motor 1M, 11M, fan motor 19M, four-way valve 12, each expansion device 3, 13, each bypass valve 7, 17, and pump 18 are driven.

The control unit 20 includes the following means (1) to (4) as main functions.
(1) At the time of activation, it is determined whether or not to execute the low outside air temperature activation mode based on the incoming water temperature Twi obtained from the detection signal of the inlet water temperature sensor 35 and the outside air temperature To obtained from the detection signal of the outside air temperature sensor 37. Low outside air temperature activation mode selection means 20a.
(2) Bypass circuit opening time setting means 20b for setting a time for opening the bypass circuits 6 and 16 according to the outside air temperature To when the low outside air temperature starting mode is executed.
(3) The high temperature side bypass control means 20c that opens the high temperature side bypass circuit 6 in accordance with the outside air temperature To when the low outside air temperature activation mode is executed.
(4) Low temperature side bypass control means 20d that opens the low temperature side bypass circuit 16 in addition to the high temperature side bypass circuit 6 in accordance with the outside air temperature To when the low outside temperature start mode is executed.

Hereinafter, the operation of the above-described binary refrigeration cycle apparatus R will be described based on FIGS.
FIG. 3 is a flowchart of processing executed by the control unit 20 of the dual refrigeration cycle apparatus R, and FIG. 4 is an explanatory diagram showing the relationship between the outside air temperature and the operation in the low outside air temperature starting mode.

The operator operates the operation unit provided on the hot water supply side or the operation unit provided in the dual refrigeration cycle apparatus R, or the operation is started according to the operation schedule set in any of the operation units. When instructed, the controller 20 first detects the incoming water temperature Twi detected by the inlet water temperature sensor 35 provided on the inlet side of the water-side flow path 2 b of the hot water heat exchanger 2 and the outside air temperature sensor 37. To obtain the outside air temperature To.
And the control part 20 is higher than predetermined | prescribed temperature Twis (for example, 40 degreeC) beforehand memorize | stored in the control part 20, and the outside temperature To is predetermined | prescribed temperature T1 (previously memorize | stored in the control part 20). It is determined whether or not the temperature is, for example, 20 ° C. (step S1).

Here, the refrigerating machine oil is easily diluted when the temperature of the refrigerating machine oil in the compressor is lowered and the refrigerant pressure is suddenly increased. When the incoming water temperature Twi is 40 ° C. or lower, the condensation pressure in the hot water heat exchanger 2 of the high temperature side refrigeration cycle Ra is not high, so the pressure in the compressor suddenly increases even when the high temperature side compressor 1 is started. There is nothing. Therefore, dilution of the refrigerating machine oil hardly occurs even when the temperature of the refrigerating machine oil is low (the outside air temperature To is low). Further, when the outside air temperature To is higher than 20 ° C., the temperature of the refrigerating machine oil in the compressor does not decrease, and therefore the condensation pressure in the hot water heat exchanger 2 of the high temperature side refrigeration cycle Ra is high (the incoming water temperature Twi is high). However, dilution of refrigeration oil is unlikely to occur. Therefore, the controller 20 does not execute the low outside air temperature activation mode when the incoming water temperature Twi is 40 ° C. or lower or the outside air temperature To is higher than 20 ° C. (in the case of No in step S1).
On the other hand, when the incoming water temperature Twi is higher than 40 ° C. and the outside air temperature To is 20 ° C. or lower (in the case of Yes in step S1), the control unit 20 executes a low outside air temperature starting mode described below.

As shown in FIG. 4, the control unit 20 controls the opening time of the bypass circuit and the opening and closing of the bypass valve according to the outside air temperature To.
First, the control unit 20 sets a bypass circuit open time (bypass circuit open set time) Ts according to the outside air temperature To.

  The controller 20 determines whether or not the outside air temperature To is within a range of predetermined values T1 to T2 (T2 <To ≦ T1) (step S3). Here, T1 is, for example, 20 ° C., and T2 is −10 ° C. If the outside air temperature To is higher than −10 ° C. and 20 ° C. or lower (in the case of Yes in step S3), the control unit 20 proceeds to step S5 and sets the opening time ts of the high temperature side bypass valve 7 of the high temperature side bypass circuit 6 to a predetermined value. Time t1 (for example, 6 minutes) is set.

In step S3, when the outside air temperature To is −10 ° C. or less (in the case of No in step S3), the control unit 20 proceeds to step S4 and the outside air temperature To is within a range of the predetermined values T2 to T3 (T3 <To ≦ It is determined whether or not T2). Here, T3 is −15 ° C., for example.
If the outside air temperature To is higher than −15 ° C. and lower than −10 ° C. (in the case of Yes in Step S4), the control unit 20 proceeds to Step S6 and opens the high-temperature side bypass valve 7 of the high-temperature side bypass circuit 6 for a time ts. Is set to a predetermined time t2 (for example, 8 minutes).

  When the outside air temperature To is −15 ° C. or lower (in the case of No in step S4), the control unit 20 proceeds to step S7 and opens the bypass valves 7 and 17 of the high temperature side bypass circuit 6 and the low temperature side bypass circuit 16. The time ts is set to a predetermined time t3 (for example, 30 minutes).

  The controller 20 starts the operation of the high temperature side compressor 1 after opening the high temperature side bypass valve 7 of the high temperature side bypass circuit 6 (step 8). Furthermore, it progresses to step S9 and the driving | operation of the low temperature side compressor 11 is started.

  When the high temperature side bypass valve 7 of the high temperature side refrigeration cycle Ra is opened and the high temperature side compressor 1 is operated, a part of the gas refrigerant discharged from the high temperature side compressor 1 passes through the high temperature side bypass circuit 6. It flows into the high temperature side accumulator 5. The gas refrigerant flowing into the high temperature side accumulator 5 is sucked into the high temperature side compressor 1 and warms the refrigeration oil in the compressor. As time elapses, the temperature of the gas refrigerant discharged from the high temperature side compressor 1 rises, and the temperature of the refrigerator oil also rises.

At this time, the control unit 20 acquires the temperature Td of the discharge gas refrigerant detected by the temperature sensor 31a, and determines whether or not the discharge gas temperature Td exceeds a predetermined temperature (step S12).
In the present embodiment, the predetermined temperature is a temperature 80 ° C. obtained by subtracting a predetermined value α (for example, 10 ° C.) from a hot water set temperature (target set temperature) Twos (for example, 90 ° C.) set by the operation unit.

When the discharged gas refrigerant temperature Td exceeds 80 ° C. (Twos−10 ° C.) in step 12S (No in step S11), the control unit 20 determines that the refrigerating machine oil in the compressor 1 has been sufficiently warmed. Then, the high temperature side bypass valve 7 is closed (step S14).
Moreover, even if the discharge gas refrigerant temperature Td does not exceed 80 ° C. (in the case of Yes in step S11), the control unit 20 sets the elapsed time t after the high-pressure side bypass circuit 6 is opened to the bypass circuit open setting. When time ts (6 minutes in step S5, 8 minutes in step S6) has elapsed (in the case of Yes in step S13), it is determined that the refrigeration oil in the compressor 1 has been warmed, and the high-temperature side bypass valve 7 is closed (step S14).

  And after closing the high temperature side bypass valve 7, the control part 20 cancels | releases the low external temperature starting mode (step S15), and transfers to a normal driving | operation.

  When the low outside air temperature start-up mode is executed, the control unit 20 drives the high temperature side compressor 1 at a constant operating frequency (for example, 30 Hz) smaller than the operating frequency during normal operation while the high temperature side bypass valve 7 is open. . If the operating frequency of the high temperature side compressor 1 is suddenly increased or driven at a high operating frequency under conditions where the refrigerating machine oil is easily diluted, the amount of refrigerating machine oil discharged outside the compressor increases. End up. Therefore, when the low outside air temperature start-up mode is executed, the amount of the refrigerating machine oil discharged to the outside of the compressor can be suppressed by maintaining the operating frequency of the high temperature side compressor 1 at 30 Hz.

  On the other hand, the low temperature side compressor 11 is driven at the same operating frequency as the normal operation because the dilution of the refrigeration oil is less likely to occur than the high temperature side compressor 1. When the low temperature side compressor 11 is also driven at a low operating frequency, the heat given to the high temperature side refrigeration cycle Ra by the low temperature side refrigeration cycle Rb is insufficient, and it takes time to start up the high temperature side refrigeration cycle Ra. Accordingly, in order to quickly raise the discharge gas temperature Td of the high temperature side compressor 1, the low temperature side compressor 11 is driven in the same manner as in the normal operation.

Next, the operation in the low outside air temperature start mode when the outside air temperature To is extremely low will be described.
When the outside air temperature To is very low, such as −15 ° C. (predetermined temperature T3), the high-temperature side refrigerant falls into the high-temperature side refrigeration cycle Ra, and the refrigerant circulation rate is reduced. Since the side bypass valve 7 is opened and the high temperature side compressor 1 is driven at a low operating frequency, the low temperature side refrigerant of the low temperature side refrigeration cycle Rb cannot completely dissipate in the cascade heat exchanger 4. Therefore, the high-pressure side pressure in the low-temperature side refrigeration cycle Rb suddenly increases, and a protective device such as a high-pressure switch acts to forcibly stop the operation of the dual refrigeration cycle device R. As described above, when the outside air temperature To is in a very low state, the dual refrigeration cycle apparatus R may not be operated.

  Therefore, in order to enable the dual refrigeration cycle apparatus R to be operated even under a situation where the outside air temperature is extremely low, the control unit 20 has a case where the outside air temperature To is lower than −15 ° C. (in the case of No in step S4). ) Sets the bypass circuit opening set time ts to 30 minutes (t3) (step S7), then opens the high temperature side bypass valve 7 (step S10) and opens the low temperature side bypass valve 17 (step S11).

  Under conditions where the outside air temperature is extremely low, the refrigerating machine oil in the high temperature side compressor 1 is difficult to warm, so the bypass circuit opening set time ts is set to 6 minutes (t1: step S5) or 8 minutes (t2: step S6). Long 30 minutes (t3) is set.

  After setting the bypass circuit opening set time ts, the high temperature side bypass valve 7 of the high temperature side bypass circuit 6 is opened by the command from the control unit 20 to start the operation of the high temperature side compressor 1 (step S10). Further, according to a command from the control unit 20, the low temperature side bypass valve 17 of the low temperature side bypass circuit 16 is opened, and the operation of the low temperature side compressor 11 is started (step S11).

  At this time, the high temperature side compressor 1 is driven at a low operating frequency (constant 30 Hz), and the low temperature side compressor 11 is driven at a normal operating frequency.

  By opening the low temperature side bypass valve 17, part of the gas refrigerant discharged from the low temperature side compressor 11 flows into the low temperature side accumulator 15 via the low temperature side bypass circuit 16. The gas refrigerant flowing into the low temperature side accumulator 15 is sucked into the low temperature side compressor 11. A part of the gas refrigerant discharged from the low-temperature side compressor 11 flows into the low-temperature side bypass circuit 16, so that a rapid increase in the high-pressure side pressure of the low-temperature side refrigeration cycle Rb can be suppressed, and the high pressure of the low-temperature side refrigeration cycle Rb. Forced stop due to abnormality can be avoided.

When the discharge gas refrigerant temperature Td of the high temperature side compressor 1 exceeds 80 ° C. (Twos−10 ° C.) (No in Step S12), the control unit 20 determines that the refrigerating machine oil in the high temperature side compressor 1 has been sufficiently warmed. Judgment is made to close the high temperature side bypass valve 6 and the low temperature side bypass valve 16 (step S14).
Further, the controller 20 does not start the high-pressure side bypass valve 7 and the low-temperature side bypass valve 17 even if the discharge gas refrigerant temperature Td does not exceed 80 ° C. (Twos−10 ° C.) (Yes in Step S12). When the elapsed time t of 30 minutes has passed (ts = t3) (Yes in step S13), it is determined that the refrigerating machine oil in the high-temperature compressor 1 has been warmed, and accordingly, the high-temperature side bypass valve 7 and the low-temperature side bypass valve 17 Is closed (step S14).

Next, the control unit 20 closes the high temperature side bypass valve 7 and the low temperature side bypass valve 17, then cancels the low outside air temperature activation mode (step S15), and shifts to normal operation.
With the above configuration, the dual refrigeration cycle apparatus R can be operated even under a situation where the outside air temperature To is extremely low.

  As described above, the binary refrigeration cycle apparatus R in the present embodiment operates the high temperature side compressor 1 with the high temperature side bypass circuit 6 opened when the outside air temperature is low and the refrigeration oil is likely to be diluted. By starting, a high-temperature gas refrigerant can be flowed into the compressor to increase the temperature of the refrigeration oil in the compressor. Accordingly, it is possible to suppress the refrigerant from being dissolved in the refrigerating machine oil, and to suppress the discharge amount of the refrigerating machine oil to the outside of the compressor due to dilution.

  Furthermore, the binary refrigeration cycle apparatus R in the present embodiment prevents a high pressure abnormality in the low temperature side cycle Rb by opening the bypass circuit 16 of the low temperature side refrigeration cycle Rb even under a situation where the outside air temperature is extremely low. be able to.

  The two-stage refrigeration cycle apparatus R according to the present invention is not limited to the hot water generating apparatus, is configured according to the application destination, and is not limited to the above-described embodiment.

  For example, instead of the air heat exchanger 14 of the low temperature side refrigeration cycle Rb, if a heat exchanger that absorbs heat from warm waste water in a factory or the like is used, the heat exchanger surface like the air heat exchanger 14 is used. Since frosting does not occur, the four-way valve 12 for making the low temperature side refrigeration cycle Rb a reverse cycle can be removed.

  The refrigerant used in the high temperature side refrigeration cycle Ra and the low temperature side refrigeration cycle Rb is not limited to R134a and R410A, and refrigerants such as R32, R245fa, HFO-1234yf, and HFO-1234ze may be used.

  As mentioned above, although this embodiment was described, the above-mentioned embodiment is shown as an example and does not intend limiting the range of embodiment. The novel embodiment can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... High temperature side compressor, 2 ... Hot water heat exchanger, 3 ... High temperature side expansion apparatus, 4 ... Cascade heat exchanger, 5 ... High temperature side accumulator, 6 ... High temperature side bypass circuit, 7 ... High temperature side bypass valve, Ra ... High temperature side refrigeration circuit, 11 ... Low temperature side compressor, 12 ... Four-way valve, 13 ... Low temperature side expansion device, 14 ... Air heat exchanger, 15 ... Low temperature side accumulator, 16 ... Low temperature side bypass circuit, 17 ... Low temperature side bypass valve DESCRIPTION OF SYMBOLS 18 ... Water pump, Rb ... Low temperature side freezing circuit, K ... Housing, 20 ... Control part (control means), 21, 22, 23 ... Inverter apparatus.

Claims (3)

A high temperature side compressor, a high temperature side condenser, a high temperature side expansion device, a cascade heat exchanger, a high temperature side refrigeration circuit communicating the high temperature side accumulator via a high temperature side refrigerant pipe;
A low temperature side compressor, a cascade heat exchanger, a low temperature side expansion device, a low temperature side evaporator, a low temperature side accumulator, and a low temperature side refrigeration circuit communicating the low temperature side accumulator via a low temperature side refrigerant pipe;
A high temperature side bypass circuit connecting the discharge side of the high temperature side compressor and the inlet side of the high temperature side accumulator, a high temperature side bypass valve provided in the high temperature side bypass circuit,
A low temperature side bypass circuit connecting the discharge side of the low temperature side compressor and the inlet side of the low temperature side accumulator; a low temperature side bypass valve provided in the low temperature side bypass circuit;
During startup, when the outside air temperature is below a first temperature, open the hot side bypass valve, when the outside air temperature is less than the first second temperature lower than the temperature, further the low temperature side bypass valve opens And a control means. Wherein, while the hot-side bypass valve is opened, according to claim 1, characterized in that to drive the high-temperature side compressor with a small predetermined operating frequency than the operating frequency during normal operation two Original refrigeration cycle equipment. Wherein the control unit includes a low outside air temperature startup mode selecting means for determining whether or not to perform a low-outside air temperature startup mode based on the temperature and the outside air temperature at the inlet side of the heated fluid in the high temperature side condenser, low Bypass circuit opening time setting means for setting the time to open the bypass circuit according to the outside air temperature when executing the outside temperature start mode, and the high temperature side bypass for opening the high temperature side bypass circuit according to the outside temperature when executing the low outside temperature start mode and control means, at low outside air temperature startup mode execution, according to claim 1 or 2 and the low temperature-side bypass control means for opening the cold-side bypass circuit in addition to the hot side bypass circuit in accordance with the outdoor temperature, comprising the to two-stage refrigeration cycle apparatus according to.

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