JP2019200013A - Refrigeration cycle device - Google Patents

Abstract

To provide a new technology to lower a pressure ratio in a refrigeration cycle device.SOLUTION: A refrigeration cycle device (100) of the disclosure includes: an evaporator (2) for evaporating a liquid phase refrigerant to generate a gas phase refrigerant; at least one turbo compressor (3) for compressing the gas phase refrigerant generated in the evaporator (2); a condenser (4) for condensing the gas phase refrigerant compressed by the turbo compressor (3); a high pressure route (8) that, when a plurality of turbo compressors (3) are provided, extends to the condenser (4) with the turbo compressor (3) having the highest discharge pressure as an original point, and, when only one turbo compressor (3) is provided, extends to the condenser (4) with the turbo compressor (3) as an original point; and a refrigerant supply passage (11) for guiding the liquid phase refrigerant from the evaporator (2) to a high pressure space (15) including a steam space inside the condenser (4) and the high pressure route (8).SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a refrigeration cycle apparatus.

  As one of technical problems of a refrigeration cycle apparatus equipped with a turbo compressor, a refrigerant reverse flow phenomenon (swirl stall) from the discharge port to the suction port of the turbo compressor is known. This phenomenon occurs when the pressure ratio in the refrigeration cycle apparatus exceeds an allowable value determined according to the rotational speed of the turbo compressor, and causes noise and shaft vibration.

  Conventionally, as a method for reducing the pressure ratio, it is known that a condenser and an evaporator are connected by a gas bypass pipe (Patent Document 1). The amount of refrigerant circulating through the cycle is increased by the gas bypass pipe, and the pressure ratio is lowered. Thereby, turning stall, that is, surging can be prevented.

Japanese Patent Laying-Open No. 2015-151991 (FIG. 1)

  However, even if the condenser and the evaporator are connected by a gas bypass pipe, the pressure ratio cannot always be reduced quickly. For example, when a refrigerant having a low density in the gas phase is used, the effect of the gas bypass pipe connecting the condenser and the evaporator is limited.

  The present disclosure provides a novel technique for reducing the pressure ratio in a refrigeration cycle apparatus.

This disclosure
An evaporator that evaporates liquid phase refrigerant to produce gas phase refrigerant;
At least one turbo compressor for compressing the gas-phase refrigerant produced in the evaporator;
A condenser for condensing the gas-phase refrigerant compressed by the turbo compressor;
When a plurality of turbo compressors are provided, the turbo compressor having the highest discharge pressure extends from the turbo compressor to the condenser, and when only one turbo compressor is provided, A high-pressure path extending from the turbo compressor to the condenser, and
A refrigerant supply path for guiding the liquid refrigerant from the evaporator toward a high-pressure space including a vapor space inside the condenser and the high-pressure path;
A refrigeration cycle apparatus is provided.

  According to the present disclosure, the pressure ratio in the refrigeration cycle apparatus can be lowered.

FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to an embodiment of the present disclosure. FIG. 2 is a graph showing the characteristics of the compressor. FIG. 3 is a flowchart of the surging prevention control. FIG. 4 is a configuration diagram of a refrigeration cycle apparatus according to a modification. FIG. 5 is a configuration diagram of a refrigeration cycle apparatus according to another modification.

(Knowledge that became the basis of this disclosure)
The technique described in Patent Document 1 is suitable for a refrigeration cycle apparatus using a Freon refrigerant having a relatively high density in a gas phase. On the other hand, a refrigerant with a low density in the gas phase has a small heat capacity in the gas phase, so that even if a gas bypass pipe is applied to a refrigeration cycle apparatus using such a refrigerant, the pressure ratio is sufficiently reduced Is difficult. Regardless of the type of refrigerant, it is desired to reliably reduce the pressure ratio to prevent or eliminate surging.

(Outline of one aspect according to the present disclosure)
The refrigeration cycle apparatus according to the first aspect of the present disclosure includes:
An evaporator that evaporates liquid phase refrigerant to produce gas phase refrigerant;
At least one turbo compressor for compressing the gas-phase refrigerant produced in the evaporator;
A condenser for condensing the gas-phase refrigerant compressed by the turbo compressor;
When a plurality of turbo compressors are provided, the turbo compressor having the highest discharge pressure extends from the turbo compressor to the condenser, and when only one turbo compressor is provided, A high-pressure path extending from the turbo compressor to the condenser, and
A refrigerant supply path for guiding the liquid refrigerant from the evaporator toward a high-pressure space including a vapor space inside the condenser and the high-pressure path;
It has.

  According to the first aspect, the pressure ratio in the refrigeration cycle apparatus can be lowered. As a result, surging can be prevented or eliminated.

  In the second aspect of the present disclosure, for example, the refrigeration cycle apparatus according to the first aspect further includes a pump disposed in the refrigerant supply path. By controlling the pump, the timing of supplying the liquid phase refrigerant to the high-pressure space can be freely controlled.

  In the third aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to the first or second aspect, the refrigerant supply path includes a supply mechanism positioned at an end portion on the discharge side. According to the supply mechanism, the pressure ratio can be quickly reduced.

  In the fourth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to the third aspect, the supply mechanism includes an atomization nozzle. If an atomization nozzle is used as the supply mechanism, the contact area between the liquid-phase refrigerant and the gas-phase refrigerant can be sufficiently increased.

  In the fifth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to the third or fourth aspect, the supply mechanism applies a velocity component parallel to a flow direction of the gas-phase refrigerant to the liquid-phase refrigerant. It arrange | positions in the said high voltage | pressure space. According to the fifth aspect, in addition to lowering the pressure ratio, the pressure of the gas-phase refrigerant discharged from the compressor can be increased by the momentum of the liquid-phase refrigerant. That is, the pressure increase width in the compressor can be reduced.

  In the sixth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to fifth aspects, the high-pressure path flows from the upstream side to the downstream side in the flow direction of the gas-phase refrigerant. It has a reduced diameter part where the road cross-sectional area is gradually reduced. According to the sixth aspect, it can be expected that the momentum of the liquid-phase refrigerant is efficiently transported to the gas-phase refrigerant and the effect of increasing the pressure is enhanced.

  In the seventh aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to sixth aspects, the rotational speed of the turbo compressor is increased in order to start the refrigeration cycle apparatus from a stopped state. When at least one operation selected from a start-up operation and a stop operation that reduces the number of revolutions of the turbo compressor to stop the refrigeration cycle apparatus is performed, the liquid phase enters the high-pressure space through the refrigerant supply path. Refrigerant is supplied. According to the seventh aspect, it is possible to reliably prevent surging from occurring when starting and stopping the refrigeration cycle apparatus.

  In the eighth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to sixth aspects, when the operating state of the turbo compressor is in a surging state or the operating state of the turbo compressor is When the transition to the surging state is predicted, the liquid-phase refrigerant is supplied to the high-pressure space through the refrigerant supply path. According to the eighth aspect, surging is immediately eliminated or the occurrence of surging can be reliably prevented.

  In the ninth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to sixth aspects, the rotation speed of the turbo compressor is equal to or lower than a threshold rotation speed, and the The liquid phase refrigerant is supplied to the high pressure space. According to the ninth aspect, it is possible to reliably prevent surging from occurring when starting and stopping the refrigeration cycle apparatus.

  In the tenth aspect of the present disclosure, for example, in the refrigeration cycle apparatus according to any one of the first to ninth aspects, the refrigerant includes a substance whose saturation vapor pressure at room temperature is a negative pressure as a main component. By applying the technique of the present disclosure to a refrigeration cycle apparatus using such a refrigerant, the pressure ratio can be sufficiently reduced, and surging can be reliably prevented.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

(Embodiment)
FIG. 1 shows a configuration of a refrigeration cycle apparatus according to an embodiment of the present disclosure. The refrigeration cycle apparatus 100 includes an evaporator 2, a compressor 3 and a condenser 4. The compressor 3 is connected to the evaporator 2 by a low pressure path 6 and is connected to the condenser 4 by a high pressure path 8. The condenser 4 is connected to the evaporator 2 by a return path 9. The evaporator 2, the compressor 3, and the condenser 4 are annularly connected in this order to constitute the refrigerant circuit 10.

  In the evaporator 2, the refrigerant evaporates to generate a gas phase refrigerant (refrigerant vapor). The gas-phase refrigerant generated in the evaporator 2 is sucked into the compressor 3 through the low-pressure path 6 and compressed. The compressed gas-phase refrigerant is supplied to the condenser 4 through the high-pressure path 8. In the condenser 4, the gas phase refrigerant is cooled to generate a liquid phase refrigerant (refrigerant liquid). The liquid phase refrigerant is sent from the condenser 4 to the evaporator 2 through the return path 9.

  In the refrigeration cycle apparatus 100, each path and each circuit can be configured by one or a plurality of pipes.

  The refrigeration cycle apparatus 100 includes, for example, a substance whose saturation vapor pressure at normal temperature (Japanese Industrial Standard: 20 ° C. ± 15 ° C./JIS Z8703) is negative (absolute pressure lower than atmospheric pressure) as a main component. Refrigerant is filled. Examples of such a refrigerant include a refrigerant containing water as a main component. The “main component” means a component that is contained most in mass ratio.

  A refrigerant containing a substance whose saturation vapor pressure at room temperature is a negative pressure as a main component has a small density in a gas phase. By applying the technology of the present disclosure to a refrigeration cycle apparatus using such a refrigerant, the pressure ratio can be sufficiently reduced, and surging can be reliably prevented or eliminated.

  The refrigeration cycle apparatus 100 further includes a heat absorption circuit 12 and a heat dissipation circuit 14.

  The heat absorption circuit 12 is a circuit for using the liquid phase refrigerant cooled by the evaporator 2 and has necessary devices such as a pump and an indoor heat exchanger. A part of the heat absorption circuit 12 is located inside the evaporator 2. In the evaporator 2, a part of the endothermic circuit 12 may be located above the liquid level of the liquid phase refrigerant or may be located below the liquid level of the liquid phase refrigerant. The heat absorption circuit 12 is filled with a heat medium such as water or brine.

  The liquid-phase refrigerant stored in the evaporator 2 comes into contact with members (piping) constituting the heat absorption circuit 12. Heat exchange is performed between the liquid refrigerant and the heat medium in the heat absorption circuit 12, and the liquid refrigerant evaporates. The heat medium in the endothermic circuit 12 is cooled by the latent heat of vaporization of the liquid refrigerant. For example, when the refrigeration cycle apparatus 100 is an air conditioner that cools a room, the room air is cooled by the heat medium of the heat absorption circuit 12. The indoor heat exchanger is, for example, a fin tube heat exchanger.

  The cooling target of the liquid refrigerant of the evaporator 2 is not limited to indoor air. The cooling target of the evaporator 2 may be a gas other than air or a liquid.

  The heat dissipation circuit 14 is a circuit used to take heat from the refrigerant inside the condenser 4 and includes necessary devices such as a pump and a cooling tower. A part of the heat dissipation circuit 14 is located inside the condenser 4. Specifically, a part of the heat dissipation circuit 14 is located above the liquid level of the liquid-phase refrigerant in the condenser 4. The heat dissipation circuit 14 is filled with a heat medium such as water or brine. When the refrigeration cycle apparatus 100 is an air conditioner that cools a room, the condenser 4 is disposed outside the room, and the refrigerant in the condenser 4 is cooled by the heat medium of the heat dissipation circuit 14.

  The high-temperature gas-phase refrigerant discharged from the compressor 3 contacts a member (pipe) constituting the heat dissipation circuit 14 inside the condenser 4. Heat exchange is performed between the gas-phase refrigerant and the heat medium inside the heat dissipation circuit 14, and the gas-phase refrigerant is condensed. The heat medium inside the heat dissipation circuit 14 is heated by the condensation latent heat of the gas-phase refrigerant. The heat medium heated by the gas-phase refrigerant is cooled by outside air or cooling water in a cooling tower (not shown) of the heat dissipation circuit 14, for example.

  The evaporator 2 is comprised by the container which has heat insulation and pressure resistance, for example. The evaporator 2 stores the liquid phase refrigerant and evaporates the liquid phase refrigerant inside. The liquid refrigerant inside the evaporator 2 absorbs heat generated from the outside of the evaporator 2 and evaporates. That is, the liquid-phase refrigerant heated by absorbing heat from the heat absorption circuit 12 evaporates in the evaporator 2. In the present embodiment, the liquid-phase refrigerant stored in the evaporator 2 indirectly contacts the heat medium circulating in the heat absorption circuit 12. That is, a part of the liquid phase refrigerant stored in the evaporator 2 is heated by the heat medium of the heat absorption circuit 12 and used to heat the liquid phase refrigerant in the saturated state. The temperature of the liquid-phase refrigerant stored in the evaporator 2 and the temperature of the gas-phase refrigerant generated in the evaporator 2 are 5 ° C., for example.

  In this embodiment, the evaporator 2 is an indirect contact type heat exchanger (for example, a shell tube heat exchanger). However, the evaporator 2 may be a direct contact type heat exchanger such as a spray type or filler type heat exchanger. That is, the liquid phase refrigerant may be heated by circulating the liquid phase refrigerant in the heat absorption circuit 12. Further, the endothermic circuit 12 may be omitted.

  The compressor 3 sucks and compresses the gas phase refrigerant generated by the evaporator 2. The compressor 3 is a speed type compressor (dynamic compressor), for example. The speed type compressor is a compressor that increases the pressure of the gas-phase refrigerant by giving momentum to the gas-phase refrigerant and then decelerating it. Examples of the speed type compressor include a centrifugal compressor, a mixed flow compressor, and an axial flow compressor. The speed type compressor is also called a turbo compressor. The compressor 3 may include a variable speed mechanism for changing the rotation speed. An example of the variable speed mechanism is an inverter that drives the motor of the compressor 3. The temperature of the refrigerant at the discharge port of the compressor 3 is, for example, in the range of 100 to 150 ° C.

  The condenser 4 is comprised by the container which has heat insulation and pressure resistance, for example. The condenser 4 condenses the gas-phase refrigerant compressed by the compressor 3 and stores the liquid-phase refrigerant generated by condensing the gas-phase refrigerant. In the present embodiment, the gas-phase refrigerant indirectly condenses and condenses on the heat medium cooled by releasing heat to the external environment. That is, the gas phase refrigerant is cooled and condensed by the heat medium of the heat dissipation circuit 14. The temperature of the gas-phase refrigerant introduced into the condenser 4 is, for example, in the range of 100 to 150 ° C. The temperature of the liquid phase refrigerant stored in the condenser 4 is, for example, 35 ° C.

  In the present embodiment, the condenser 4 is an indirect contact heat exchanger (for example, a shell tube heat exchanger). However, the condenser 4 may be a direct contact type heat exchanger such as a spray type or filler type heat exchanger. That is, the liquid phase refrigerant may be cooled by circulating the liquid phase refrigerant in the heat dissipation circuit 14. Further, the heat dissipation circuit 14 may be omitted.

  The low pressure path 6 is a flow path for guiding the gas phase refrigerant from the evaporator 2 to the compressor 3. The outlet of the evaporator 2 is connected to the suction port of the compressor 3 through the low pressure path 6.

  The high-pressure path 8 is a flow path for guiding the gas-phase refrigerant compressed from the compressor 3 to the condenser 4. The discharge port of the compressor 3 is connected to the inlet of the condenser 4 through the high pressure path 8.

  In the present embodiment, only one compressor 3 is provided. The high pressure path 8 is a flow path extending from the compressor 3 to the condenser 4.

  The return path 9 is a flow path for guiding the liquid phase refrigerant from the condenser 4 to the evaporator 2. The evaporator 2 and the condenser 4 are connected by the return path 9. A valve 17 is arranged in the return path 9. The valve 17 may be an on-off valve or a flow rate adjustment valve. Other components such as a pump and a sensor may be arranged in the return path 9.

  The refrigeration cycle apparatus 100 further includes a sensor 20. In the present embodiment, the sensor 20 is attached to the evaporator 2. The sensor 20 may be a temperature sensor, a pressure sensor, or both of them. When the sensor 20 is a temperature sensor, the sensor 20 detects the temperature of the liquid-phase refrigerant or the gas-phase refrigerant in the evaporator 2. That is, the sensor 20 can detect the evaporation temperature in the evaporator 2. When the sensor 20 is a pressure sensor, the sensor 20 detects the pressure inside the evaporator 2. That is, the sensor 20 can detect the saturated vapor pressure in the evaporator 2.

  The refrigeration cycle apparatus 100 further includes a sensor 21. In the present embodiment, the sensor 21 is attached to the condenser 4. The sensor 21 may be a temperature sensor, a pressure sensor, or both of them. When the sensor 21 is a temperature sensor, the sensor 21 detects the temperature of the liquid-phase refrigerant or the gas-phase refrigerant in the condenser 4. That is, the sensor 21 can detect the condensation temperature in the condenser 4. When the sensor 21 is a pressure sensor, the sensor 21 detects the pressure inside the condenser 4. That is, the sensor 21 can detect the saturated vapor pressure in the condenser 4.

  The sensor 20 may be disposed in the low pressure path 6. The sensor 21 may be disposed in the high pressure path 8.

  Examples of the temperature sensor include a temperature sensor using a thermistor, a temperature sensor using a thermocouple, and the like. Examples of the pressure sensor include a capacitive pressure sensor, a resistance wire pressure sensor, and a piezoresistive pressure sensor.

  The refrigeration cycle apparatus 100 further includes a refrigerant supply path 11. The refrigerant supply path 11 is a flow path that guides the liquid phase refrigerant from the evaporator 2 toward the high-pressure space 15. In the example shown in FIG. 1, the refrigerant supply path 11 connects the evaporator 2 and the high-pressure path 8. Alternatively, the refrigerant supply path 11 may connect the evaporator 2 and the vapor space inside the condenser 4. Further, the refrigerant supply path 11 may be branched, and each of the branched refrigerant supply paths 11 may be connected to the high-pressure path 8 and the vapor space inside the condenser 4. The high-pressure space 15 is a space including the vapor space inside the condenser 4 and the high-pressure path 8. “Vapor space inside the condenser 4” means a space above the liquid level of the liquid-phase refrigerant stored in the condenser 4. The inlet of the refrigerant supply path 11 is located below the evaporator 2. According to such a configuration, the low-temperature liquid phase refrigerant can be stably supplied to the high-pressure space 15 through the refrigerant supply path 11. The “lower part of the evaporator 2” means a part below the liquid level of the liquid refrigerant stored in the evaporator 2.

  When the low-temperature liquid phase refrigerant stored in the evaporator 2 is supplied to the high-pressure space 15 through the refrigerant supply path 11, the liquid-phase refrigerant comes into contact with the high-temperature gas phase refrigerant discharged from the compressor 3. Allow the refrigerant to condense. Thereby, the condensation temperature, that is, the condensation pressure can be lowered. By reducing the condensation pressure, the pressure ratio can be lowered. According to the present disclosure, the effect of reducing the pressure ratio can be sufficiently obtained even when a refrigerant having a low density in the gas phase is used.

  The “pressure ratio” is the ratio of the pressure (discharge pressure) at the discharge port to the pressure (suction pressure) at the suction port of the compressor 3. The pressure ratio can be calculated from detection values obtained from one or more sensors. For example, when both the sensors 20 and 21 are pressure sensors, the pressure ratio can be calculated by dividing the detection value of the sensor 21 by the detection value of the sensor 20. When the sensors 20 and 21 are temperature sensors, the saturated vapor pressure can be calculated from the temperature of the liquid refrigerant, and the pressure ratio can be calculated from the saturated vapor pressure. Since control is often performed so that the temperature of the liquid-phase refrigerant stored in the evaporator 2 is constant, the pressure ratio can also be estimated from the condensation temperature (detected value of the sensor 21) in the condenser 4. is there. The method for calculating the pressure ratio is not particularly limited.

  A pump 16 is disposed in the refrigerant supply path 11. By controlling the pump 16, the timing of supplying the liquid phase refrigerant to the high pressure space 15 can be freely controlled. The pump 16 is, for example, a positive displacement pump such as a piston pump, a plunger pump, a gear pump, or a vane pump. The pump 16 may be a pump that can change the supply flow rate. In this case, it is easy to supply the liquid refrigerant to the high-pressure space 15 at an appropriate flow rate according to the operating state of the refrigeration cycle apparatus 100.

  The refrigerant supply path 11 has a supply mechanism 11a located at the end on the discharge side. The supply mechanism 11 a has a role of increasing the surface area of the liquid-phase refrigerant and increasing the contact area between the liquid-phase refrigerant and the gas-phase refrigerant discharged from the compressor 3. According to the supply mechanism 11a, the pressure ratio can be quickly reduced.

  The structure of the supply mechanism 11a is not particularly limited. The supply mechanism 11a is, for example, an atomization nozzle that atomizes and supplies liquid phase refrigerant. If an atomizing nozzle is used as the supply mechanism 11a, the contact area between the liquid-phase refrigerant and the gas-phase refrigerant can be sufficiently increased. Examples of the atomizing nozzle include an ultrasonic atomizing nozzle, a swirl flow type atomizing nozzle, and a collision type atomizing nozzle. The ultrasonic atomizing nozzle is a spray nozzle that atomizes a liquid using ultrasonic waves. A swirl-type atomizing nozzle is a spray nozzle that atomizes a liquid using centrifugal force. The collision type atomizing nozzle is a spray nozzle that atomizes a liquid by colliding with an obstacle (target).

  The discharge direction (spraying direction) of the liquid phase refrigerant from the supply mechanism 11a may be parallel to or perpendicular to the flow direction of the vapor phase refrigerant. The discharge direction of the liquid phase refrigerant may intersect the flow direction of the gas phase refrigerant.

  Further, the supply mechanism 11 a may be configured to flow the liquid phase refrigerant along the inner surface of the high-pressure path 8, or may be configured to flow the liquid phase refrigerant along the inner surface of the condenser 4. .

  Other components such as a valve and a sensor may be arranged in the refrigerant supply path 11.

  The refrigeration cycle apparatus 100 further includes a controller 22. The controller 22 is, for example, a DSP (Digital Signal Processor) including an A / D conversion circuit, an input / output circuit, an arithmetic circuit, a storage device, and the like. Detection signals from measuring devices such as the sensor 20 and the sensor 21 are input to the controller 22. The controller 22 controls controlled objects such as the compressor 3, the pump 16, and the valve 17 based on the measurement results of various measuring devices. The controller 22 stores a program for appropriately operating the refrigeration cycle apparatus 100.

  The controller 22 may include an inverter that drives the compressor 3, and may include an inverter that drives the pump 16. The controller 22 may be constituted by a single microcomputer or a plurality of microcomputers. Furthermore, the refrigeration cycle apparatus 100 may have a plurality of controllers.

  The controller 22 acquires a sensor signal from the sensor 20 and / or the sensor 21, and specifies a pressure ratio (discharge pressure / intake pressure) in the refrigeration cycle apparatus 100 from the acquired sensor signal. The controller 22 specifies the operating state of the compressor 3 based on the specified pressure ratio and the flow rate (mass flow rate) of the refrigerant in the compressor 3, and if necessary, enters the liquid phase into the high-pressure space 15 through the refrigerant supply path 11. An electrical process for supplying the refrigerant is executed. The flow rate of the refrigerant can be estimated from the rotational speed of the compressor 3. In general, when the turbo compressor is operated at a sufficiently high rotational speed, the flow rate is approximately proportional to the rotational speed. The “sufficiently large number of revolutions” depends on the design of the turbo compressor.

  Surging occurs when the pressure ratio exceeds an allowable value when the turbo compressor is operated at a specific speed. There is a certain restriction between the rotational speed of the turbo compressor and the pressure ratio, and surging occurs when the turbo compressor is operated outside the restriction.

  FIG. 2 shows the characteristics of the compressor 3. The graph of FIG. 2 is stored in the memory of the controller 22 in the form of a lookup table, for example. The region defined by the solid curve P is a region where the compressor 3 can be operated normally without causing surging and choking. When the pressure ratio increases and the operating state of the compressor 3 deviates from the region defined by the curve P, that is, when the operating state of the compressor 3 is in the surging state, the liquid is supplied to the high-pressure space 15 through the refrigerant supply path 11. Phase refrigerant can be supplied. In consideration of safety, when the operating state of the compressor 3 deviates from the region defined by the dashed curve P1, that is, when the operating state of the compressor 3 is predicted to shift to the surging state, the refrigerant supply path The liquid phase refrigerant may be supplied to the high-pressure space through 11. In this way, surging can be eliminated immediately or the occurrence of surging can be reliably prevented.

  When the set of the flow rate and the pressure ratio in the curve P is an allowable value of the compressor 3, regarding surging, the pressure ratio in the curve P1 can be set to a value lower than the allowable value. For example, when compared at the same flow rate, the pressure ratio in the curve P1 is about 1% to 10% smaller than the pressure ratio in the curve P.

  When the rotation speed of the compressor 3 is larger than a predetermined threshold rotation speed (for example, 20,000 rotations / min), the flow rate of the refrigerant is determined according to the rotation speed of the compressor 3. Therefore, the operating state of the compressor 3 can be determined using the rotation speed of the compressor 3. Specifically, the flow rate of the refrigerant is determined according to the suction pressure and the rotation speed of the compressor 3. Based on the suction pressure, the discharge pressure, and the rotation speed of the compressor 3, the operating state of the compressor 3 can be specified. The “threshold rotation speed” is a design value of the compressor 3. The rotational speed of the compressor 3 is a value that is always stored in the memory of a controller (for example, the controller 22) for controlling the motor of the compressor 3.

  When the refrigeration cycle apparatus 100 is started from a stopped state and when the refrigeration cycle apparatus 100 is stopped, the rotational speed of the compressor 3 is lower than the threshold rotational speed. Therefore, the start-up operation for increasing the rotation speed of the compressor 3 to start the refrigeration cycle apparatus 100 from the stop state and the stop operation for decreasing the rotation speed of the compressor 3 to stop the refrigeration cycle apparatus 100 are selected. When at least one operation is performed, the liquid-phase refrigerant may be supplied to the high-pressure space 15 through the refrigerant supply path 11. Thereby, it is possible to reliably prevent surging from occurring when the refrigeration cycle apparatus 100 is started and stopped. “Stopped state” means, for example, a state where the rotational speed of the compressor 3 is zero.

  The pressure ratio varies according to the magnitude of the load, the outside air temperature, and the like. When the refrigeration cycle apparatus 100 is stopped by reducing the rotation speed of the compressor 3 from the rated operation or the partial load operation, it is necessary to decrease the rotation speed of the compressor 3 from a state where the pressure ratio is high. There is a possibility that the rate of decrease in the pressure ratio cannot follow the rate of decrease in the rotational speed, and the operating state of the compressor 3 shifts to the surging region. Therefore, when an instruction to stop the operation is given to the refrigeration cycle apparatus 100 (for example, when the stop switch is turned on), the liquid phase refrigerant is supplied to the high-pressure space 15 through the refrigerant supply path 11 to sufficiently reduce the pressure ratio. After that, the rotational speed of the compressor 3 may be decreased. In this way, the refrigeration cycle apparatus 100 can be smoothly and safely stopped without causing surging.

  When the rotation speed of the compressor 3 is a threshold rotation speed (for example, 20,000 rotations / min) or less, the refrigerant does not flow sufficiently. This phenomenon is remarkable when the internal pressure of the refrigeration cycle apparatus 100 is lower than atmospheric pressure. Therefore, when the rotation speed of the compressor 3 is equal to or lower than the threshold rotation speed, the liquid phase refrigerant can be supplied to the high-pressure space 15 through the refrigerant supply path 11. Thereby, it is possible to reliably prevent surging from occurring when the refrigeration cycle apparatus 100 is started and stopped.

  Next, control for preventing surging will be described.

  After the start-up switch of the refrigeration cycle apparatus 100 is turned on, the controller 22 executes the surging prevention control shown in FIG. 3 as necessary.

  In step S1, it is determined whether or not the current rotational speed of the compressor 3 is equal to or greater than a threshold rotational speed. When the rotation speed of the compressor 3 is less than the threshold rotation speed, the pump 16 is operated in step S4. Thereby, the liquid phase refrigerant is supplied to the high-pressure space 15, and the pressure ratio can be lowered. As a result, surging can be prevented.

  If the rotation speed of the compressor 3 is greater than or equal to the threshold rotation speed, it is determined in step S2 whether or not the current pressure ratio is less than or equal to the threshold pressure ratio. If the pressure ratio exceeds the threshold pressure ratio, the pump 16 is operated in step S4. Thereby, the liquid phase refrigerant is supplied to the high-pressure space 15, and the pressure ratio can be lowered. As a result, surging is prevented. The threshold pressure ratio corresponds to, for example, the curve P1 described with reference to FIG. 2, and is determined according to the rotation speed (flow rate) of the compressor 3.

  When the rotation speed of the compressor 3 is equal to or higher than the threshold rotation speed and the pressure ratio is equal to or lower than the threshold pressure ratio, the pump 16 is stopped in step S3. Thereby, it can avoid that the performance and efficiency of the refrigerating-cycle apparatus 100 fall more than necessary.

  As described above, when the stop switch of the refrigeration cycle apparatus 100 is turned on, the pump 16 may be operated immediately without performing the control shown in FIG.

(Modification)
FIG. 4 shows a configuration of a refrigeration cycle apparatus according to a modification. In the refrigeration cycle apparatus 200, the supply mechanism 11a is disposed in the high-pressure space 15 so as to impart a velocity component parallel to the flow direction of the gas-phase refrigerant to the liquid-phase refrigerant. Specifically, the discharge direction (spraying direction) of the liquid phase refrigerant from the supply mechanism 11a substantially matches the flow direction of the gas phase refrigerant. According to such a configuration, in addition to lowering the pressure ratio, the pressure of the gas-phase refrigerant discharged from the compressor 3 can be increased by the momentum of the liquid-phase refrigerant. That is, the pressure increase width in the compressor 3 can be reduced. Such a configuration is particularly effective during high load operation. Examples of the high load operation include operation under a high outside air temperature condition and operation under a high pressure ratio condition.

  In this modification, the high-pressure path 8 has a reduced diameter portion 8a in which the cross-sectional area of the flow path gradually decreases (continuously) from the upstream side to the downstream side in the flow direction of the gas-phase refrigerant. The supply mechanism 11a sprays the liquid phase refrigerant toward the high-pressure space 15 of the reduced diameter portion 8a. According to such a configuration, it can be expected that the momentum of the liquid-phase refrigerant is efficiently transported to the gas-phase refrigerant and the effect of increasing the pressure is enhanced.

  The flow path cross-sectional area of the vapor space of the condenser 4 is larger than the flow path cross-sectional area of the high-pressure path 8. For this reason, the cross-sectional area of the flow path rapidly increases at the connection portion between the reduced diameter portion 8 a and the condenser 4. It can be expected that the vapor space of the condenser 4 functions as a diffuser that restores static pressure.

  FIG. 5 shows a configuration of a refrigeration cycle apparatus according to another modification. The refrigeration cycle apparatus 300 is different from the refrigeration cycle apparatus 100 described with reference to FIG. 1 in that it includes a plurality of compressors.

  The refrigeration cycle apparatus 300 further includes a second compressor 13 in addition to the compressor 3 (hereinafter referred to as “first compressor 3”). The first compressor 3 and the second compressor 13 are connected in series. In other words, the first compressor 3 and the second compressor 13 are arranged so that the gas-phase refrigerant compressed by the first compressor 3 is further compressed by the second compressor 13. The intermediate pressure path 7 connects the discharge port of the first compressor 3 and the suction port of the second compressor 13.

  In this modification, the high-pressure path 8 extends to the condenser 4 starting from the second compressor 13 that is a compressor having the highest discharge pressure. A path connecting the first compressor 3 and the second compressor 13 is an intermediate pressure path 7. Also in this modification, the liquid phase refrigerant is supplied to the high-pressure path 8 at an appropriate timing. This reduces the pressure ratio and prevents surging.

  The refrigeration cycle apparatus disclosed in this specification is useful for an air conditioner, a chiller, a heat storage device, and the like.

2 Evaporator 3 Compressor (first compressor)
4 condenser 6 low pressure path 7 intermediate pressure path 8 high pressure path 8a reduced diameter portion 9 return path 10 refrigerant circuit 11 refrigerant supply path 11a supply mechanism 12 heat absorption circuit 13 second compressor 14 heat dissipation circuit 15 high pressure space 16 pump 17 valve 20, 21 Sensor 22 Controller 100, 200, 300 Refrigeration cycle apparatus

Claims (10)

An evaporator that evaporates liquid phase refrigerant to produce gas phase refrigerant;
At least one turbo compressor for compressing the gas-phase refrigerant produced in the evaporator;
A condenser for condensing the gas-phase refrigerant compressed by the turbo compressor;
When a plurality of turbo compressors are provided, the turbo compressor having the highest discharge pressure extends from the turbo compressor to the condenser, and when only one turbo compressor is provided, A high-pressure path extending from the turbo compressor to the condenser, and
A refrigerant supply path for guiding the liquid refrigerant from the evaporator toward a high-pressure space including a vapor space inside the condenser and the high-pressure path;
A refrigeration cycle apparatus comprising:   The refrigeration cycle apparatus according to claim 1, further comprising a pump disposed in the refrigerant supply path.   The refrigeration cycle apparatus according to claim 1, wherein the refrigerant supply path has a supply mechanism located at an end portion on a discharge side.   The refrigeration cycle apparatus according to claim 3, wherein the supply mechanism includes an atomization nozzle.   The refrigeration cycle apparatus according to claim 3 or 4, wherein the supply mechanism is disposed in the high-pressure space so as to impart a velocity component parallel to the flow direction of the gas-phase refrigerant to the liquid-phase refrigerant.   The said high pressure path | route has a diameter-reduced part from which the flow-path cross-sectional area is gradually reducing toward the downstream from the upstream in the flow direction of the said gaseous-phase refrigerant | coolant. Refrigeration cycle equipment.   Selected from start operation for increasing the rotation speed of the turbo compressor to start the refrigeration cycle apparatus from a stopped state, and stop operation for decreasing the rotation speed of the turbo compressor to stop the refrigeration cycle apparatus The refrigeration cycle apparatus according to claim 1, wherein the liquid-phase refrigerant is supplied to the high-pressure space through the refrigerant supply path when at least one operation is performed.   When the operation state of the turbo compressor is in the surging state or when the operation state of the turbo compressor is predicted to shift to the surging state, the liquid phase refrigerant is supplied to the high pressure space through the refrigerant supply path. The refrigeration cycle apparatus according to any one of claims 1 to 6.   The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein when the rotation speed of the turbo compressor is equal to or less than a threshold rotation speed, the liquid-phase refrigerant is supplied to the high-pressure space through the refrigerant supply path. .   The refrigeration cycle apparatus according to any one of claims 1 to 9, wherein the refrigerant includes a substance whose saturation vapor pressure at room temperature is a negative pressure as a main component.

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