JP2014228147A - Refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerator which achieves reduction in power consumption, and which secures reliability.SOLUTION: In a refrigerator, a high-pressure heat exchanger 11, a first decompression part 21, a gas-liquid separator 22, a second decompression part 23, a first low pressure heat exchanger 24 and a first compression part 25 are connected so that a cooling medium can circulate, and it is configured so that the cooling medium branched between the first decompression part 21 and the gas-liquid separator 22 flows to the high-pressure heat exchanger 11 via a second low pressure heat exchanger 26 and a second compression part 27 for compressing at least one of the cooling media flowing out of the second low pressure heat exchanger 26 and the gas-liquid separator 22. It also includes: selection parts 28, 29 for selecting the destination for the cooling medium to flow in from the first decompression part 21 from among the gas-liquid separator 22 and the second low pressure heat exchanger 26; and a control part which performs control of the first compression part 25 and the second compression part 27 and control of the flow-in destination of the cooling medium by the selection parts 28, 29, which stops the first compression part 25 and operates the second compression part 27 and which at least performs control during low load with the flow-in destination of the cooling medium being the second low pressure heat exchanger 26.

Description

  The present invention is used to cool a large number of electronic devices such as servers and computers constituting an information technology device (hereinafter referred to as “IT device”) and an information communication technology device (hereinafter referred to as “ICT device”). The present invention relates to a refrigerator used.

  In the data center, a large number of electronic devices such as IT servers and ICT devices, such as servers and computers, are arranged on the floor, and refrigerators and air conditioning systems that process heat generated from these electronic devices are used. ing.

  Many of these air-conditioning systems and the like adopt a vapor compression refrigeration cycle. There is a need for an air conditioning system having a high cooling capacity or a high cooling capacity because a large amount of heat is generated from the electronic equipment and there is a risk that normal operation of the electronic equipment cannot be secured if the temperature rises excessively. Simply trying to realize an air conditioning system having a high cooling capacity or the like increases the power consumed by the air conditioning system or the like.

  In view of the recent trend to reduce power consumption, it is desirable to use an air conditioning system with high cooling capacity while suppressing an increase in power consumption. In other words, an air conditioning system with high cooling efficiency is required. In order to meet such a demand, for example, an air conditioner employing a gas injection cycle has been proposed (see, for example, Patent Document 1).

JP 2000-106995 A

  In general, when designing an air conditioning system or the like, the cooling load is set so as to be able to cope with the maximum expected thermal load (in other words, a design assumed cooling load). Here, it is designed as an air conditioning system capable of processing the maximum amount of heat generated from electronic equipment.

  Since the air conditioning system and the like designed in this way are limited when the maximum amount of heat is generated from the electronic device, the air conditioning system is rarely operated in a state where a design assumed cooling load is applied. Further, since the cooling load varies depending on the season, the situation in which the air conditioning system is operated in a state where the assumed design cooling load is applied is further limited.

  In order to stably operate an air conditioning system or the like, it is necessary to operate in a state where a predetermined cooling load is applied. If it is operated in a low load state where the load is lower than a predetermined cooling load, the air conditioning system or the like is intermittently operated (starting and stopping is repeated). High reliability is required for an air conditioning system or the like used for cooling electronic equipment in a data center or the like as compared with those used for other applications. Therefore, there is a demand for an air conditioning system that can stably operate continuously regardless of the cooling load state.

  However, as described above, when operated in a low load state where the load is lower than the predetermined cooling load, the air conditioning system and the like repeatedly start and stop, and it is difficult to continuously maintain the predetermined temperature. was there.

  The present invention has been made in order to solve the above-described problem, and is a refrigerator that can reduce power consumption and maintain reliability at a predetermined temperature continuously. The purpose is to provide.

In order to achieve the above object, the present invention provides the following means.
The refrigerator according to the present invention includes a high-pressure heat exchanger that cools a high-pressure refrigerant and a high-pressure refrigerant that is cooled by the high-pressure heat exchanger in a refrigeration apparatus that moves low-temperature heat to a high-temperature side. 1 decompression unit, a gas-liquid separator that separates the low-pressure refrigerant decompressed by the first decompression unit into a gas refrigerant and a refrigerant liquid, and a first decompression unit that further depressurizes the liquid refrigerant separated by the gas-liquid separator. 2 decompression section, a first low pressure heat exchanger that evaporates the refrigerant decompressed by the second decompression section, and compresses the refrigerant flowing out from the first low pressure heat exchanger toward the high pressure heat exchanger A first compression section that discharges; a second low-pressure heat exchanger that evaporates the low-pressure refrigerant decompressed by the first decompression section; a refrigerant that has flowed out of the second low-pressure heat exchanger; and the gas-liquid Before compressing at least one of the gaseous refrigerant separated by the separator A second compression section that discharges between the first compression section and the high-pressure heat exchanger; and a destination to which the low-pressure refrigerant decompressed by the first decompression section flows is the gas-liquid separator and the second low-pressure heat. A selection unit selected from an exchanger, control of operation stop of the first compression unit and the second compression unit, and control of an inflow destination of the low-pressure refrigerant by the selection unit, A control unit that stops at least one compression unit, operates the second compression unit, and performs at least low-load time control with the selection unit configured to make the low-pressure refrigerant flow into the second low-pressure heat exchanger. It is characterized by being.

  According to the refrigerator of the present invention, when the cooling capacity required for the refrigerator is low, it is possible to reduce power consumption in the refrigerator by the control unit performing low load control. In the low load control, since the control to stop the first compression unit and operate the second compression unit is performed, the compression unit is compared with the case where both the first compression unit and the second compression unit are operated. The power consumed is reduced. In addition, the second compression unit used in the injection cycle has a lower capacity than the first compression unit, and can operate at a higher load factor than the first compression unit when the air conditioning system has a low load. Can be operated with higher efficiency than operating with a low load. Therefore, the power consumed during operation is small. As a result, in low-load control performed when the cooling capacity required for the refrigerator is low, it is easy to reduce power consumption by operating only the second compression unit.

  Moreover, it becomes possible for a control part to operate a refrigerator stably by performing control at the time of low load, and it can aim at ensuring of the reliability of a refrigerator. In the low load control, the first compressor is stopped and the second compressor is operated, so that the cooling of the refrigerator is performed as compared with the case where both the first compressor and the second compressor are operated. Capability is unlikely to be excessive. Furthermore, when the second compression unit is operated, the mass flow rate of the refrigerant discharged from the second compression unit is reduced compared to the case where the first compression unit is operated, so that the cooling capacity of the refrigerator is excessive. Hard to become. In other words, the cooling capacity when the refrigerator is continuously operated can be reduced, and the refrigerator can be continuously operated without starting and stopping even when the required cooling capacity is small.

In the above invention, it is preferable that the second compression section has a smaller compression capacity of the refrigerant than the first compression section.
Thus, by making the compression capacity of the second compression section smaller than the compression capacity of the first compression section, it becomes easier to further reduce the power consumption in the refrigerator and to maintain the predetermined temperature continuously. It becomes easy to ensure reliability. In general, the power consumed by the compression unit decreases as the compression capacity decreases. Therefore, it becomes easy to reduce the electric power consumed in the low load control by reducing the compression capacity of the second compression unit operated in the low load control. In addition, since the cooling capacity when the refrigerator is continuously operated in the low load control is further reduced, it is easy to continuously operate the refrigerator without starting and stopping even when the required cooling capacity is small. . In addition, since the 2nd compression part compresses the refrigerant | coolant (refrigerant which does not flow through a 1st low pressure heat exchanger) which does not contribute to the air_conditioning | cooling capability of a refrigerator when low load time control is not performed, it is 1st The compression capacity can be set smaller than that of the compression unit.

  In the above-described invention, the control unit includes a difference in air temperature before and after heat exchange in the heat exchanger performing heat exchange among the first low-pressure heat exchanger and the second low-pressure heat exchanger, and the first The required cooling capacity based on the flow rate of the air heat exchanged by the low pressure heat exchanger, and the first heat exchanger or the first flow rate when the flow rate of the refrigerant discharged from the first compression unit is the minimum flow rate. The first air temperature after the heat exchange with the two heat exchangers is obtained, the first air temperature after the heat exchange is compared with a predetermined air temperature, and the first air temperature after the heat exchange is the predetermined air When it is determined that the temperature is equal to or lower than the temperature, it is preferable to execute the low load control.

  Thus, by determining whether or not to execute the low load control based on the first air temperature after heat exchange and the predetermined air temperature, an increase in the amount of calculation required for the determination can be suppressed. For example, the amount of computation required for the determination increases when the power consumption when the low load control is executed is compared with the power consumption when the low load control is not executed to determine whether or not the low load control is executed. . Therefore, by performing the above-described determination based on the first air temperature after heat exchange and the predetermined air temperature, it is possible to suppress an increase in calculation load on the control unit.

  In the above-described invention, the control unit includes a difference in air temperature before and after heat exchange in the heat exchanger performing heat exchange among the first low-pressure heat exchanger and the second low-pressure heat exchanger, and the first The required cooling capacity based on the flow rate of the air heat exchanged by the low pressure heat exchanger, and the first heat exchanger or the first flow rate when the flow rate of the refrigerant discharged from the second compression unit is the maximum flow rate. The second air temperature after the heat exchange with the two heat exchangers is obtained, the second air temperature after the heat exchange is compared with a predetermined air temperature, and the second air temperature after the heat exchange is the predetermined air When it is determined that the temperature is equal to or lower than the temperature, at least the power consumption when the first compression unit is operated is compared with the power consumption when only the second compression unit is operated, and only the second operation unit is operated. When it is determined that the power consumption is small It is preferable to perform the low-load control.

  Thus, it is determined whether or not to execute the low load control based on the second air temperature after heat exchange, the predetermined air temperature, and the power consumption of the first compression unit and the second compression unit. Thereby, the power consumption of a refrigerator can be suppressed more reliably. Specifically, the second air temperature after heat exchange is equal to or lower than a predetermined air temperature, and the power consumption when only the second compression unit is operated is less than when the first compression unit is operated. Only during low load control. Therefore, it is possible to ensure the reliability of the refrigerator while reliably suppressing the power consumption of the refrigerator.

  In the above invention, the control unit compares the second air temperature after the heat exchange and a predetermined air temperature, determines that the second air temperature after the heat exchange is equal to or lower than the predetermined air temperature, and then at least the Before comparing the power consumption when operating the first compression unit and the power consumption when operating only the second compression unit, the required cooling capacity based on the difference in the air temperature and the flow rate of the air, and the After the heat exchange, the first air temperature after heat exchange with the first heat exchanger or the second heat exchanger when the flow rate of the refrigerant discharged from the first compression unit is the minimum flow rate is obtained. The first air temperature and the predetermined air temperature are compared, and when it is determined that the first air temperature after the heat exchange is equal to or lower than the predetermined air temperature, the power consumption of the first compression unit and the first air temperature 2 Determine the power consumption of the compression unit It not, the it is preferable to perform a low-load control.

  As described above, when the first air temperature after heat exchange is equal to or lower than the predetermined air temperature, the amount of calculation in the control unit is suppressed by executing the low load control without determining the power consumption. be able to. Specifically, if the refrigerator can satisfy the required cooling capacity only by the operation of the second compression section, and the cooling capacity of the refrigerator becomes excessive in the operation of the first compression section, the power consumption is reduced. It is necessary to execute low load control regardless of the size. In such a case, the calculation for comparing the power consumption can be omitted, and the calculation amount in the control unit can be suppressed by omitting the calculation.

  In the above invention, the control unit may control the air temperature before heat exchange or after heat exchange in the heat exchanger performing heat exchange among the first low pressure heat exchanger and the second low pressure heat exchanger. It is determined that a temperature difference that is a difference between the measured value and a predetermined set value of the air temperature is less than a predetermined threshold, and the flow rate of the refrigerant discharged from the first compression unit is the minimum flow rate. In this case, it is preferable to execute the low load control.

  In this way, a material for determining whether or not to perform low-load control that the temperature difference that is the difference between the measured value of the air temperature before or after heat exchange and a predetermined set value is less than a predetermined threshold value. As a result, it is possible to reduce the amount of calculation performed in the control unit when performing the determination, as compared with the determination method using estimation of required cooling capacity and power consumption. Furthermore, whether the flow rate of the refrigerant discharged from the first compression unit is the minimum flow rate, in other words, the operation frequency of the first compression unit is the minimum frequency, is used as a determination material for determining whether to perform the low load control. Thus, the refrigerator can be operated stably. That is, it is possible to suppress the first compression unit from being started and stopped and to operate the refrigerator stably.

  In the above invention, before the control unit obtains at least the necessary cooling capacity, before the heat exchange is performed in the heat exchanger performing heat exchange among the first low-pressure heat exchanger and the second low-pressure heat exchanger. Or the measured value of the air temperature after heat exchange is compared with a preset value of the air temperature, the measured value is lower than the set value, and the measured value It is preferable to obtain at least the necessary cooling capacity after it is determined that the difference between the value and the set value is equal to or greater than a predetermined threshold.

  Thus, only when the measured value and the set value of the air temperature satisfy a predetermined relationship, the number of times the calculation related to the determination is performed is suppressed by determining whether or not the low load control is executed. can do. Specifically, if the measured value is lower than the set value and the difference between the measured value and the set value is greater than or equal to a predetermined threshold, it is estimated that the cooling capacity of the refrigerator exceeds the required cooling capacity. Therefore, the determination of whether or not to execute the low load control is started. On the other hand, if the measured value is greater than or equal to the set value, or if the difference between the measured value and the set value is less than the predetermined threshold, the cooling capacity of the refrigerator may not exceed the required cooling capacity. It is estimated that there is no need to execute the low load control. By performing the determination based on the measurement value and the set value that are easy to calculate compared to the determination of whether or not to execute the low load control, the amount of calculation in the control unit can be suppressed.

  In the above invention, when the control unit determines that the pressure ratio, which is the ratio of the suction side pressure and the discharge side pressure of the first compression unit and the second compression unit, is equal to or less than a predetermined pressure ratio, It is preferable to perform control to stop the operation of the second compression unit.

  When the pressure ratio, which is the value obtained by dividing the value of the discharge side pressure in the first and second compression parts by the value of the suction side pressure, becomes equal to or less than the predetermined pressure ratio, the operation of the second compression part is stopped. By doing so, the pressure ratio in the first and second compression sections can be kept larger than the predetermined pressure ratio. As a result, it is possible to suppress the first and second compression units from repeatedly starting and stopping and to operate stably.

  According to the refrigerator of the present invention, when the cooling capacity required for the refrigerator is low, the power consumption is reduced by performing the low load control in which the first compressor is stopped and the second compressor is operated. In addition, there is an effect that reliability can be ensured.

It is a mimetic diagram explaining the composition of the air-conditioning system concerning a 1st embodiment of the present invention. It is a block diagram explaining the structure of the control part in FIG. It is a circuit diagram explaining the state at the time of normal operation in the air conditioning system of FIG. It is a circuit diagram explaining the state at the time of normal operation with the low external temperature of an air conditioning system. 3 is a flowchart for explaining processing for determining which of normal control and low load control is executed in the control unit of FIG. 2. It is a circuit diagram explaining the state of the low load operation in an air conditioning system. It is a block diagram explaining the other structural example in the control part of FIG. It is a flowchart explaining the other Example of the determination process in the control part of FIG. It is a flowchart explaining the process which determines which of normal control and control at the time of low load is performed in the control part of the air conditioning system which concerns on 2nd Embodiment of this embodiment. It is a schematic diagram explaining the range in which normal control and low load control are performed. It is a flowchart explaining the other Example of the determination process in the control part of FIG. It is a flowchart explaining the process which determines which of normal control and low load time control is performed in the control part of the air-conditioning system which concerns on 3rd Embodiment of this embodiment. It is a flowchart explaining another Example of the flowchart of FIG. It is a block diagram explaining the structure in the case of controlling a 1st compressor and a 2nd compressor by a pressure ratio.

[First Embodiment]
Hereinafter, an air conditioning system (refrigerator) 1 according to a first embodiment of the present invention will be described with reference to FIGS. The air conditioning system 1 of the present embodiment is used for air conditioning of a data center, and processes a large amount of heat generated from electronic devices such as servers and computers arranged on the floor of the data center.

  The outdoor unit 10 of the air conditioning system 1 is arranged outdoors, for example, in contact with outside air such as the roof of a data center, and the indoor unit 20 is arranged on a floor on which electronic devices such as servers are arranged, and indoor air on the floor It is arranged so that it can be cooled. In FIG. 1, for ease of explanation, an example in which one outdoor unit 10 and one indoor unit 20 are provided is described. However, a plurality of indoor units 20 are provided for one outdoor unit 10. It may be provided, and a plurality of indoor units 20 may be provided for a plurality of outdoor units 10, and the number of units is not particularly limited.

  As shown in FIG. 1, the air conditioning system 1 includes a condenser (high pressure heat exchanger) 11 disposed in the outdoor unit 10, a first expansion valve (first decompression unit) 21 disposed in the indoor unit 20, Gas-liquid separator 22, second expansion valve (second decompression unit) 23, first evaporator (first low-pressure heat exchanger) 24, first compressor (first compression unit) 25, second evaporator (second 2 low-pressure heat exchanger) 26, second compressor (second compression unit) 27, first control valve (selection unit) 28, second control valve (selection unit) 29, and control unit 40. Has been.

  The condenser 11 is a heat exchanger into which a high-temperature and high-pressure gaseous refrigerant discharged from at least one of the first compressor 25 and the second compressor 27 flows, and releases the heat of the flowing-in refrigerant to the outside air to condense. Is. Outside air is guided to the condenser 11 by a blowing means (not shown) such as a fan provided in the outdoor unit 10. As the condenser 11, a known type of heat exchanger can be used, and the type is not particularly limited.

  The first expansion valve 21 is disposed between the condenser 11, the gas-liquid separator 22 and the second evaporator 26, expands the refrigerant condensed by the condenser 11, and reduces the pressure thereof. It is something to be made. The second expansion valve 23 is disposed between the gas-liquid separator 22 and the first evaporator 24, expands the liquid refrigerant supplied from the gas-liquid separator 22, and further reduces the pressure. Is. As the 1st expansion valve 21 and the 2nd expansion valve 23, a well-known expansion valve or a pressure-reduction mechanism can be used, The form etc. are not specifically limited. In the present embodiment, the first expansion valve 21 and the second expansion valve 23 are mechanisms for adjusting the degree of pressure reduction so that the refrigerant flowing out of the first evaporator 24 and the second evaporator 26 has a desired superheat. The description will be made by applying to those having

  The gas-liquid separator 22 is a container that is disposed between the first expansion valve 21, the second expansion valve 23, and the second compressor 27. The gas-liquid separator 22 is a gas-liquid two-layer decompressed by the first expansion valve 21. The refrigerant flows in and separates the gas refrigerant and the liquid refrigerant. A pipe connected from the gas-liquid separator 22 to the second expansion valve 23 is connected to an area below the gas-liquid separator 22 where liquid refrigerant is stored. On the other hand, the pipe connected from the gas-liquid separator 22 to the second compressor 27 is connected to a region above the gas-liquid separator 22 and where the gaseous refrigerant exists.

  The first evaporator 24 is a heat exchanger disposed between the second expansion valve 23 and the first compressor 25, and exchanges heat between the refrigerant decompressed by the second expansion valve 23 and room air. Is to do. The second evaporator 26 is a heat exchanger disposed between the first expansion valve 21 and the second compressor 27, and exchanges heat between the refrigerant decompressed by the first expansion valve 21 and room air. Is to do. The refrigerant flowing into the first evaporator 24 or the second evaporator 26 is evaporated by absorbing the heat of the room air and becomes a gaseous refrigerant. On the other hand, the temperature of the indoor air is lowered because the heat is taken away by the refrigerant.

  Indoor air is guided to the first evaporator 24 and the second evaporator 26 by a blowing means such as a blowing fan provided in the indoor unit 20. Therefore, the indoor air that has increased in temperature by absorbing heat generated from the electronic devices that constitute the ICT device or the like is sucked into the indoor unit 20 and cooled by the first evaporator 24 and the second evaporator 26. The cooled room air is blown out from the indoor unit 20 into the room.

  The first compressor 25 is disposed between the first evaporator 24 and the condenser 11, sucks and compresses the gaseous refrigerant flowing out from the first evaporator 24, and directs the high-temperature and high-pressure refrigerant toward the condenser 11. Are discharged. The second compressor 27 is disposed between the second evaporator 26 and the gas-liquid separator 22 and the condenser 11, and is separated by the gas refrigerant flowing out from the second evaporator 26 and the gas-liquid separator 22. At least one of the gaseous refrigerant is sucked and compressed, and a high-temperature and high-pressure refrigerant is discharged between the condenser 11 and the first compressor 25. The compression volume for compressing the refrigerant of the second compressor 27 is smaller than the compression volume of the first compressor 25.

  On the discharge side of the first compressor 25, a check valve 25A for preventing the reverse flow of the refrigerant is arranged, and on the discharge side of the second compressor 27, a check valve 27A for preventing the reverse flow of the refrigerant is arranged. The check valve 25 </ b> A prevents the refrigerant from flowing back from the second compressor 27 and the condenser 11 to the first compressor 25 when the first compressor 25 is stopped. Similarly, the check valve 27A prevents the refrigerant from flowing back from the first compressor 25 or the condenser 11 to the second compressor 27 when the second compressor 27 is stopped.

  In the present embodiment, the first compressor 25 and the second compressor 27 will be described as applied to an example of a fixed capacity compressor driven by an electric motor whose rotational speed is controlled within a predetermined range by inverter control. . The first compressor 25 and the second compressor 27 are controlled based on a control signal output from the control unit 40 described later. More specifically, the operation of the first compressor 25 and the second compressor 27 is controlled by controlling the electric motor by inverter control based on the control signal. As the first compressor 25 and the second compressor 27, those of a known format can be used, and the format is not particularly limited.

  The first control valve 28 and the second control valve 29 control the inflow destination of the refrigerant decompressed by the first expansion valve 21. The first control valve 28 is a pipe connecting the first expansion valve 21 and the second evaporator 26, and is disposed between the branch point where the pipe extending to the gas-liquid separator 22 branches and the second evaporator 26. Open / close valve. The second control valve 29 is an on-off valve disposed between the aforementioned branch point and the gas-liquid separator 22. In the present embodiment, the opening and closing of the first control valve 28 and the second control valve 29 will be described as applied to an example in which the first control valve 28 and the second control valve 29 are controlled by actuator means such as a servo motor provided in each. The operation of this actuator means is controlled based on a control signal input from the control unit 40 described later.

  Note that, as in the present embodiment, the first control valve 28 and the second control valve 29 which are on-off valves are provided, and the gas-liquid separator 22 and the second control point where the refrigerant depressurized by the first expansion valve 21 flows are provided. It may be controlled to one of the evaporators 26, or the destination into which the refrigerant flows may be controlled using one three-way valve instead of using two on-off valves, and is not particularly limited.

  The control unit 40 controls the operating state of the air conditioning system 1 and is a microcomputer having a CPU (Central Processing Unit), ROM, RAM, input / output interface, and the like. For example, as shown in FIG. 1, the place where the control unit 40 is disposed may be a place other than the indoor unit 20 and the outdoor unit 10, or may be inside the indoor unit 20, and is not particularly limited. Absent.

  As shown in the schematic diagram of FIG. 2, the control program stored in the ROM or the like causes the CPU to function as the calculation unit 41 and causes the ROM or the like to function as the storage unit 42. The control of the operation state by the control unit 40 can be exemplified by control using the temperature of room air performed in a conventional air conditioning system as a set temperature, control at low load, which is a feature of the present embodiment, and the like.

  The control unit 40 includes an outdoor air temperature sensor 32 that measures the outdoor air temperature, a suction temperature sensor 33 that measures the temperature of the indoor air that is sucked into the indoor unit 20, and a heat exchanger that is blown out from the indoor unit 20. A blowout temperature sensor 34 for measuring the temperature of the indoor air and a measurement signal indicating the temperature measured from the blowout temperature sensor 34 are input. Further, the control unit 40 receives a signal indicating the rotational frequency of the indoor fan from the indoor fan unit 31 that causes the indoor unit 20 to suck indoor air and blow out the indoor air after heat exchange.

  The control unit 40 mainly outputs a control signal for controlling the operating state of the first compressor 25 and the second compressor 27 and a control signal for controlling opening and closing of the first control valve 28 and the second control valve 29. Has been. In addition to these control signals, the control unit 40 also outputs control signals related to control performed in the conventional air conditioning system, such as a control signal for controlling the rotation frequency of the indoor fan in the indoor fan unit 31.

  Next, control and the like in the air conditioning system 1 having the above configuration will be described. Specifically, control during normal operation and low-load control during low-load operation, which is a feature of the present embodiment, will be described. Note that the normal operation means at least the operation of the air conditioning system 1 that operates the first compressor 25, and the low load operation means that the operation of the first compressor 25 is stopped and the second compressor is operated. It means the operation of the air conditioning system 1 that operates only 27.

  First, normal operation of the air conditioning system 1 will be described with reference to the circuit diagrams of FIGS. 3 and 4. At this time, the control unit 40 outputs a control signal for closing the valve to the first control valve 28 and also outputs a control signal for opening the valve to the second control valve 29. In the drawing, black indicates a state in which the valve is closed, and white indicates a state in which the valve is opened.

  When the pressure ratio of the second compressor 27 is higher than a predetermined value, the control unit 40 outputs control signals for operating the first compressor 25 and the second compressor 27 as shown in FIG. To do. Here, the predetermined value is a value with which the second compressor 27 can stably operate, and can be exemplified by a value of about 1.2.

  Note that the pressure ratio of the second compressor 27 may be directly obtained based on a measured value of a sensor or the like, or may be estimated based on the temperature of the outside air that affects the pressure ratio. As a method of estimating the pressure ratio from the outside air temperature, a map showing the relationship between the outside air temperature and the pressure ratio obtained by a method such as an experiment may be used, or an arithmetic expression obtained theoretically may be used. Good.

  The high-temperature and high-pressure gas refrigerant discharged from the first compressor 25 and the second compressor 27 exchanges heat with the outside air in the condenser 11 to release heat. The refrigerant that has released the heat condenses into a liquid refrigerant, flows out of the condenser 11, and travels toward the first expansion valve 21. The high-pressure liquid refrigerant is decompressed by the first expansion valve 21 to become a gas-liquid two-phase refrigerant.

  The gas-liquid two-phase refrigerant flows into the gas-liquid separator 22 via the opened second control valve 29 and is separated into a gas refrigerant and a liquid refrigerant. The liquid refrigerant is further depressurized by the second expansion valve 23 from the gas-liquid separator 22 and flows into the first evaporator 24. Note that the gas-liquid two-phase refrigerant does not flow into the second evaporator 26 because the first control valve 28 is closed. In the figure, the second evaporator 26 is represented by a dotted line to indicate that no refrigerant is flowing.

  In the first evaporator 24, the refrigerant absorbs the heat of the indoor air introduced by the indoor fan unit 31. The liquid refrigerant evaporates by the absorbed heat and becomes a gaseous refrigerant. On the other hand, indoor air is cooled by taking heat away and blown out to the floor by the indoor fan unit 31. The gaseous refrigerant that has flowed out of the first evaporator 24 is sucked into the first compressor 25, compressed, and discharged as a high-temperature and high-pressure refrigerant that has been pressurized to a predetermined pressure.

  On the other hand, the gas refrigerant separated by the gas-liquid separator 22 is sucked into the second compressor 27 and compressed. The compressed refrigerant is discharged from the second compressor 27, merged with the refrigerant discharged from the first compressor 25, and flows into the condenser 11.

  The control unit 40 compares the input set temperature of the room air with the temperature of the room air measured by the suction temperature sensor 33, and controls the air conditioning system 1 so that the temperature of the room air becomes the set temperature. . For example, when it is determined that the temperature of the room air is higher than the set temperature, control for increasing the cooling capacity of the air conditioning system 1 is performed. Specifically, the air conditioning system 1 is configured to increase the rotational frequency of the indoor fan in the indoor fan unit 31 to increase the flow rate of the indoor air to be heat-exchanged, and to increase the operating frequency of the first compressor 25 and the second compressor 27. The control etc. which increase the flow volume of the refrigerant | coolant which circulates are performed.

  Moreover, when it determines with the temperature of indoor air being lower than preset temperature, control which suppresses the cooling capability of the air conditioning system 1 is performed. More specifically, the air-conditioning system 1 is controlled by reducing the rotational frequency of the indoor fan in the indoor fan unit 31 to reduce the flow rate of indoor air to be heat-exchanged, and reducing the operating frequency of the first compressor 25 and the second compressor 27. The control etc. which reduce the flow volume of the refrigerant | coolant which circulates are performed.

  When the pressure ratio of the second compressor 27 is less than or equal to a predetermined value, the control unit 40 operates only the first compressor 25 and stops the operation of the second compressor 27 as shown in FIG. Output a control signal. Examples of the case where the pressure ratio is equal to or less than a predetermined value include cases where the outside air temperature has decreased due to seasonal changes, and cases where the heat load of the air conditioning system 1 has decreased.

  When the second compressor 27 is stopped, the gas refrigerant separated in the gas-liquid separator 22 is not sucked into the second compressor 27. In the figure, the second compressor 27 is indicated by a dotted line, indicating that the second compressor 27 is stopped, and the circuit between the gas-liquid separator 22 and the second compressor 27 is indicated by a dotted line so that no refrigerant is flowing. Is shown. Since the flow of the refrigerant in the air conditioning system 1 in this state is the same as that shown in FIG. 3 except that the second compressor 27 is stopped, the description thereof is omitted.

  While the air-conditioning system 1 is in operation, the control unit 40 controls at least the normal operation in which the first compressor 25 is operated, and the first compressor 25 is stopped and only the second compressor 27 is operated. The process of determining which of the on-load controls is executed is repeatedly performed.

The above-described determination is performed according to the flowchart shown in FIG.
First, the calculation unit 41 of the control unit 40 determines whether or not the temperature of the indoor air blown out from the indoor unit 20 has changed (S11). Specifically, with respect to the set temperature of the indoor air stored in the storage unit 42, the blowing temperature output from the blowing temperature sensor 34 is changed by a predetermined temperature difference (for example, −1 ° C.) for a predetermined period (for example, 5 minutes) or more. ) It is determined whether or not the above difference has occurred.

When it is determined that the blowing temperature has not changed (in the case of NO), the calculation unit 41 repeatedly performs the determination of S11.
On the other hand, when it determines with the blowing temperature having changed (in the case of YES), the calculating part 41 performs the calculation process which estimates required cooling capacity (S12). Specifically, it is calculated from the temperature difference between the intake air temperature output from the intake temperature sensor 33, the temperature of the blown air output from the blowout temperature sensor 34, and the rotation frequency of the indoor fan in the indoor fan unit 31. Necessary cooling capacity is estimated based on the air flow rate and the correction coefficient.

  In addition, a well-known formula can be used as a calculation formula used for estimation of required cooling capacity. Further, the required cooling capacity may be obtained by calculation using an arithmetic expression, or a map showing the correspondence between the temperature difference, the air flow rate, etc. and the required cooling capacity is obtained in advance, and the required cooling capacity is calculated using the map. You may ask for it. Further, the map obtained in advance may be compared with the measured value, and the map value may be automatically updated at predetermined intervals based on the measured value.

  When the required cooling capacity is estimated, the calculation unit 41 performs a process of determining whether or not the first compressor 25 can cope (S13). That is, when the first compressor 25 is operated at the lowest frequency, the temperature of the air blown from the indoor unit 20 (first air temperature) is the temperature of the blown air (predetermined value) corresponding to the set value of the indoor air. The process of determining whether or not the air temperature is equal to or lower than that is executed.

  The temperature of the air blown out when the first compressor 25 is operated at a predetermined frequency is estimated as follows. The calculation unit 41 acquires the temperature of the outside air from the outside air temperature sensor 32, the temperature of the intake air from the suction temperature sensor 33, the rotation frequency of the indoor fan from the indoor fan unit 31, and the pipe length from the storage unit 42. Here, the pipe length is the length of the pipe through which the refrigerant of the air conditioning system 1 flows, and is a value stored in the storage unit 42 in advance when the air conditioning system 1 is installed in the data center.

  Thereafter, the calculation unit 41 obtains an air volume that is the flow rate of the indoor air that is heat-exchanged by the indoor unit 20 from the rotation frequency of the indoor fan. Further, when the first compressor 25 is operated at a predetermined frequency based on the outside air temperature, the intake air temperature, the air flow rate, the pipe length, and the required cooling capacity calculated in S12, the indoor unit A process of determining whether or not the temperature of the air blown from 20 is equal to or lower than the temperature of the blown air corresponding to the set value of the room air is executed.

  Note that the processing of S13 may be performed by arithmetic processing based on a predetermined arithmetic expression, or the outside air temperature, the intake air temperature, the air volume, the pipe length, the required cooling capacity, the set value of the indoor air, and the like. May be obtained in advance and a determination may be made using a map based on these relationships.

  When it is determined that the first compressor 25 can cope with the determination in S13 (in the case of YES), in other words, the operating frequency of the first compressor 25 is equal to or higher than the minimum frequency, and the air blown out from the indoor unit 20 When it is determined that the temperature of the blown air corresponding to the set value of the indoor air can be maintained, or even if the operating frequency of the second compressor 27 is the highest frequency, the air blown from the indoor unit 20 When it is determined that the temperature of the blown air corresponding to the set value of the room air cannot be maintained, the control unit 40 performs control to operate with the first compressor 25 (S14). In other words, the air conditioning system 1 is controlled during normal operation. In this case, at least the first compressor 25 is operated as described above, and the first control valve 28 is closed and the second control valve 29 is opened. Thereafter, the process returns to S11 again, and the above-described processing is repeatedly executed.

  On the other hand, when it is determined that the first compressor 25 cannot cope (in the case of NO), in other words, even if the operating frequency of the first compressor 25 is set to the lowest frequency, the temperature of the air blown out from the indoor unit 20 Is lower than the temperature of the blown air corresponding to the set value of the room air, and when it is determined that the first compressor 25 repeats starting and stopping, the control unit 40 executes control to operate with the second compressor 27. (S15). In other words, the air conditioning system 1 is controlled in an operation at a low load. The control at low load will be described in detail below. Thereafter, the process returns to S11 again, and the above-described processing is repeatedly executed.

  Next, the case where the air-conditioning system 1 is controlled at a low load will be described with reference to FIG. When the control at the time of low load is started, the control unit 40 outputs a stop control signal to the first compressor 25 and outputs an operation control signal to the second compressor 27. Further, a control signal for opening the valve is output to the first control valve 28, and a control signal for closing the valve is output to the second control valve 29.

  The high-temperature and high-pressure gaseous refrigerant discharged from the second compressor 27 releases heat to the outside air and condenses in the condenser 11. The condensed liquid refrigerant is decompressed in the first expansion valve 21 to become a gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant flows into the second evaporator 26 through the opened first control valve 28. On the other hand, since the second control valve 29 is closed, the refrigerant does not flow into the gas-liquid separator 22, the first expansion valve 21, the first evaporator 24, and the first compressor 25. In the figure, these elements are drawn with dotted lines to indicate that no refrigerant flows.

  The refrigerant that has flowed into the second evaporator 26 absorbs heat from the indoor air introduced by the indoor fan unit 31 to evaporate into a gaseous refrigerant. The indoor air is cooled by the heat taken away by the refrigerant, and then blown out from the indoor unit 20 to the floor. The evaporated gaseous refrigerant is sucked into the second compressor 27, compressed, and discharged as a high-temperature and high-pressure refrigerant whose pressure has been increased to a predetermined pressure.

  In the operation at the time of low load, the control is performed so that the temperature of the indoor air on the floor becomes the set temperature as in the normal operation. Specifically, by controlling the rotation frequency of the indoor fan in the indoor fan unit 31 and the operation frequency of the second compressor 27, control is performed so that the temperature of the indoor air on the floor becomes the set temperature.

  According to the air conditioning system 1 having the above configuration, when the cooling capacity required for the air conditioning system 1 is low, the control unit 40 performs the low load control so that the power consumption in the air conditioning system 1 can be reduced. In the low load control, the first compressor 25 is stopped and the second compressor 27 is operated. Therefore, compared with the case where both the first compressor 25 and the second compressor 27 are operated. This reduces the power consumed by the compressor. Furthermore, the second compressor 27 used in the injection cycle has a lower capacity than the first compressor 25, and can be operated at a higher load factor than the first compressor 25 when the air conditioning system 1 has a low load. The first compressor 25 can be operated with higher efficiency than when operating at a low load. Therefore, the power consumed during operation is small. Therefore, in the low load control performed when the cooling capacity required for the air conditioning system 1 is low, it is easy to reduce power consumption by using only the second compressor 27 as the compressor to be operated.

  Moreover, it becomes possible for the control part 40 to operate the air conditioning system 1 stably by performing the control at the time of low load, and the reliability of the air conditioning system 1 can be secured. In the low load control, the first compressor 25 is stopped and the second compressor 27 is operated. Therefore, compared with the case where both the first compressor 25 and the second compressor 27 are operated. The cooling capacity of the air conditioning system 1 is unlikely to be excessive. Further, when the second compressor 27 is operated as compared with the case where the first compressor 25 is operated, the mass flow rate of the refrigerant discharged from the second compressor 27 is reduced. Capability is unlikely to be excessive. In other words, the cooling capacity when the air-conditioning system 1 is continuously operated can be reduced, and even if the required cooling capacity is small, the air-conditioning system 1 can be continuously operated without starting and stopping. .

  By making the compression capacity of the second compressor 27 smaller than the compression capacity of the first compressor 25, it becomes easier to further reduce power consumption in the air conditioning system 1 and to further ensure reliability. In general, the power consumed by a compressor decreases as its compression capacity decreases. Therefore, by reducing the compression capacity of the second compressor 27 operated in the low load control, it becomes easy to reduce the power consumed in the low load control. Further, since the cooling capacity when the air-conditioning system 1 is continuously operated in the low load control is further reduced, the air-conditioning system 1 is continuously operated without being started and stopped even when the required cooling capacity is small. It becomes easy. In addition, since the 2nd compressor 27 compresses the refrigerant | coolant (refrigerant which does not flow through the 1st evaporator 24) which does not contribute to the air_conditioning | cooling capability of the air conditioning system 1 when normal control is performed, the 1st compressor Compared to 25, the compression capacity can be set small.

  It is determined whether or not to execute the low load control based on the temperature of the blown air when the first compressor 25 is operated at the lowest frequency and the temperature of the blown air corresponding to the set value of the room air. As a result, an increase in the amount of calculation required for the determination can be suppressed. For example, the amount of calculation required for the determination increases when the power consumption when the low load control is executed is compared with the power consumption when the low load control is not executed to determine whether or not the low load control is executed. Therefore, by making the above-described determination based on the temperature of the blown air when the first compressor 25 is operated at the lowest frequency and the temperature of the blown air corresponding to the set value of the room air, the controller 40 This increase in calculation load can be suppressed.

  By performing the determination in S13 only when it is determined in S11 that the blow-out temperature has changed, the number of calculations related to the determination in S13 can be suppressed. Specifically, if the difference between the set temperature of the room air and the blowout temperature output from the blowout temperature sensor 34 exceeds a predetermined temperature difference for a predetermined period or more, the cooling capacity of the air conditioning system 1 is increased. Since it is estimated that the required cooling capacity is exceeded, the determination in S13 is started. On the other hand, when there is no difference of a predetermined temperature difference or more with respect to the set temperature of the indoor air, the temperature is not continued for a predetermined period even if there is a difference of a predetermined temperature or more. In this case, there is a possibility that the cooling capacity of the air conditioning system 1 does not exceed the required cooling capacity, and it is estimated that it is not necessary to execute the low load control. The amount of calculation in the control unit 40 can be suppressed by first performing the determination of S11 that is easier to calculate than the determination of whether or not to execute the low load control.

  As in the above-described embodiment, when performing the determination in S13, the determination may be made based on the outside air temperature, the intake air temperature, the air flow rate, the pipe length, and the required cooling capacity, or in the block diagram of FIG. As shown, a humidity sensor 35 that measures the humidity of the air sucked into the indoor unit 20 may be further provided, and the determination of S13 may be performed by adding the measured humidity.

  Further, as in the above-described embodiment, when the determination of S11 is performed, it may be determined whether or not the temperature of the indoor air blown out from the indoor unit 20 has changed, as shown in the flowchart of FIG. Alternatively, it may be determined whether the temperature of the indoor air sucked into the indoor unit 20 has changed (S11a).

  Specifically, with respect to the set temperature of the indoor air stored in the storage unit 42, the suction temperature output from the suction temperature sensor 33 is changed by a predetermined temperature difference (for example, −1 ° C.) for a predetermined period (for example, 5 minutes) or more. ) The determination may be made based on whether or not the above difference has occurred.

[Second Embodiment]
Next, an air conditioning system according to a second embodiment of the present invention will be described with reference to FIGS. The basic configuration of the air conditioning system of the present embodiment is the same as that of the first embodiment, but the first embodiment is a process for determining whether to perform normal control or low load control in the control unit. Is different. Therefore, in this embodiment, control in a control part is demonstrated using FIGS. 9-11, and description of another component etc. is abbreviate | omitted.

  The control unit 40 of the air conditioning system 1 according to the present embodiment, during the normal operation in which at least the operation of the first compressor 25 is performed while the air conditioning system 1 is being operated, similarly to the control unit 40 of the first embodiment. And the process of determining which of the low load control in which the first compressor 25 is stopped and only the second compressor 27 is operated is executed.

The above-described determination is performed according to the flowchart shown in FIG.
First, the calculation unit 41 of the control unit 40 determines whether or not the temperature of the indoor air blown out from the indoor unit 20 has changed (S11). When it is determined that the blowing temperature has not changed (in the case of NO), the calculation unit 41 repeatedly performs the determination of S11.

On the other hand, when it determines with the blowing temperature having changed (in the case of YES), the calculating part 41 performs the calculation process which estimates required cooling capacity (S12).
When the required cooling capacity is estimated, the calculation unit 41 executes a process of determining whether or not the second compressor 27 can cope (S21). That is, when the second compressor 27 is operated at the maximum frequency, the temperature of the air blown from the indoor unit 20 (second air temperature) is the temperature of the blown air (predetermined value) corresponding to the set value of the indoor air. A process for determining whether or not (air temperature) can be satisfied is executed.

  The temperature of the air blown out when the second compressor 27 is operated at a predetermined frequency is estimated as follows. The calculation unit 41 acquires the temperature of the outside air from the outside air temperature sensor 32, the temperature of the intake air from the suction temperature sensor 33, the rotation frequency of the indoor fan from the indoor fan unit 31, and the pipe length from the storage unit 42. Here, the pipe length is the length of the pipe through which the refrigerant of the air conditioning system 1 flows, and is a value stored in the storage unit 42 in advance when the air conditioning system 1 is installed in the data center.

  Thereafter, the calculation unit 41 obtains an air volume that is the flow rate of the indoor air that is heat-exchanged by the indoor unit 20 from the rotation frequency of the indoor fan. Further, when the second compressor 27 is operated at a predetermined frequency based on the outside air temperature, the intake air temperature, the air flow rate, the pipe length, and the required cooling capacity calculated in S12, the indoor unit A process of determining whether or not the temperature of the air blown from 20 satisfies the temperature of the blown air corresponding to the set value of the room air is executed.

  Note that the processing of S21 may be performed by arithmetic processing based on a predetermined arithmetic expression, or the outside air temperature, the intake air temperature, the air flow rate, the pipe length, the required cooling capacity, the set value of the indoor air, etc. May be obtained in advance and a determination may be made using a map based on these relationships.

  When it is determined that the second compressor 27 can cope with the determination in S21 (in the case of YES), in other words, the temperature of the air blown out from the indoor unit 20 corresponds to the set value of the indoor air. When it determines with satisfy | filling, the calculating part 41 performs the process which determines whether the 1st compressor 25 can respond (S13).

  When it is determined that the first compressor 25 can cope with the determination in S13 (in the case of YES), in other words, the operating frequency of the first compressor 25 is equal to or higher than the minimum frequency, and the air blown out from the indoor unit 20 When it is determined that the temperature of the blown air corresponding to the set value of the indoor air can be maintained, or the operating frequency of the second compressor 27 is equal to or lower than the maximum frequency, and the temperature of the air blown from the indoor unit 20 Is determined to be able to maintain the temperature of the blown air corresponding to the set value of the room air, the control unit 40 uses the power consumed by the first compressor 25 as the power consumed by the second compressor 27. A process of determining whether or not is the following is executed (S22). In other words, a process of determining whether or not the power consumption when the control during the normal operation is performed on the air conditioning system 1 is equal to or less than the power consumption when the low load control is performed is executed.

  Specifically, the power consumed by the first compressor 25 and the power consumed by the second compressor 27 are estimated as follows. The calculation unit 41 acquires the temperature of the outside air from the outside air temperature sensor 32, the temperature of the intake air from the suction temperature sensor 33, the rotation frequency of the indoor fan from the indoor fan unit 31, and the pipe length from the storage unit 42. Thereafter, the calculation unit 41 obtains an air volume that is the flow rate of the indoor air that is heat-exchanged by the indoor unit 20 from the rotation frequency of the indoor fan.

  Furthermore, based on the outside air temperature, the intake air temperature, the air flow rate, the pipe length, and the required cooling capacity calculated in S12, the temperature of the air blown from the indoor unit 20 becomes the set value of the indoor air. The electric power consumed by the first compressor 25 and the electric power consumed by the second compressor 27 to satisfy the corresponding blown air temperature are obtained.

  Note that the calculation processing of S22 may be performed by calculation processing based on a predetermined calculation formula, or outside air temperature, intake air temperature, air flow rate, pipe length, required cooling capacity, and set values for indoor air It may be a process of acquiring a correspondence relationship with the above in advance and using a map based on these relationships.

  When it is determined in S22 that the power consumed by the first compressor 25 is equal to or less than the power consumed by the second compressor 27 (in the case of YES), or the second compressor 27 cannot cope with in S21. Is determined (in the case of NO), the control unit 40 executes control to operate with the first compressor 25 (S14). In other words, the air conditioning system 1 is controlled during normal operation. Thereafter, the process returns to S11 again, and the above-described processing is repeatedly executed.

  On the other hand, if it is determined in S22 that the power consumed by the first compressor 25 is larger than the power consumed by the second compressor 27 (in the case of NO), the first compressor is determined in S13. When it is determined that it is not possible to respond at 25 (in the case of NO), the control unit 40 performs control to operate with the second compressor 27 (S15). In other words, the air conditioning system 1 is controlled in an operation at a low load. Thereafter, the process returns to S11 again, and the above-described processing is repeatedly executed.

  Note that the control during the normal operation and the flow of the refrigerant, the control during the low load operation and the flow of the refrigerant in the air conditioning system 1 are the same as the control and the flow of the refrigerant in the first embodiment, and the description thereof. Is omitted.

  When the range in which the low load control is performed in the present embodiment is compared with the range in the first embodiment, it is as shown in FIG. In FIG. 10, the horizontal axis represents the compression capacity of the compressor in the air conditioning system 1 or the cooling capacity of the air conditioning system 1, and the vertical axis represents the efficiency.

  In the first embodiment, even when both the normal control and the low load control are applicable, the normal control is preferentially applied, whereas in the second embodiment, the low load is applied. The difference is that the low load control is prioritized in the range where the efficiency in the time control is higher than the efficiency in the normal control.

  As in the above embodiment, the temperature of the blown air when the second compressor 27 is operating at the maximum frequency, the temperature of the blown air corresponding to the set value of the room air, the first compressor 25 and the second compressor By determining whether or not to execute the low load control based on the power consumption of the compressor 27, the power consumption of the air conditioning system 1 can be more reliably suppressed. Specifically, the temperature of the blown air when the second compressor 27 is operating at the maximum frequency is equal to or lower than the temperature of the blown air corresponding to the set value of the room air, and only the second compressor 27 is turned on. The low load control is executed when the power consumption during operation is less than when the first compressor 25 is operated. Therefore, the reliability of the air conditioning system 1 can be ensured while reliably suppressing the power consumption of the air conditioning system 1.

  When the temperature of the blown air when the first compressor 25 is operating at the lowest frequency is equal to or lower than the temperature of the blown air corresponding to the set value of the room air, the load is low without determining the power consumption By executing the time control, the amount of calculation in the control unit 40 can be suppressed. Specifically, when the air conditioning system 1 can satisfy the required cooling capacity only by the operation of the second compressor 27 and the cooling capacity of the refrigerator becomes excessive in the operation of the first compressor 25, It is necessary to execute low load control regardless of power consumption. In such a case, the calculation for comparing the power consumption can be omitted. By omitting the calculation, the amount of calculation in the control unit 40 can be suppressed, and quick control can be performed.

  Similar to the first embodiment, the humidity sensor 35 that measures the humidity of the air sucked into the indoor unit 20 and the humidity sensor that measures the humidity of the air blown from the indoor unit 20 when performing the determination of S13. 36 may be further provided, and the determination of S13 may be performed by adding the measured humidity (see FIG. 7).

  Furthermore, when performing the determination of S11, it may be determined whether the temperature of the indoor air blown out from the indoor unit 20 has changed, or as shown in the flowchart of FIG. It may be determined whether the temperature of the indoor air has changed (S11a).

[Third Embodiment]
Next, an air conditioning system according to a third embodiment of the present invention will be described with reference to FIG. The basic configuration of the air conditioning system of the present embodiment is the same as that of the first embodiment, but the first embodiment is a process for determining whether to perform normal control or low load control in the control unit. Is different. Therefore, in this embodiment, control in a control part is demonstrated using FIG. 12, and description of other components is abbreviate | omitted.

  The control unit 40 of the air conditioning system 1 according to the present embodiment, during the normal operation in which at least the operation of the first compressor 25 is performed while the air conditioning system 1 is being operated, similarly to the control unit 40 of the first embodiment. And the process of determining which of the low load control in which the first compressor 25 is stopped and only the second compressor 27 is operated is executed.

The above-described determination is performed according to the flowchart shown in FIG.
First, the calculation unit 41 of the control unit 40 determines whether or not the temperature of the indoor air blown out from the indoor unit 20 has changed (S11). When it is determined that the blowing temperature has not changed (in the case of NO), the calculation unit 41 repeatedly performs the determination of S11.

  On the other hand, when it is determined that the blowing temperature has changed (in the case of YES), the calculation unit 41 executes a calculation process for determining whether or not the blowing temperature difference is equal to or greater than a predetermined threshold (S31). ). That is, a calculation process is first performed to obtain a blowing temperature difference that is a difference between the temperature of the blowing air measured by the blowing temperature sensor 34 and a preset value stored in the storage unit 42. Thereafter, a determination process is performed to determine whether or not the obtained blowing temperature difference is equal to or greater than a threshold value stored in advance in the storage unit 42.

  In the determination of S31, when it is determined that the blowing temperature difference is less than the predetermined threshold (in the case of NO), the calculation unit 41 determines whether or not the operating frequency of the first compressor 25 is the lowest frequency. Is executed (S32).

  In the determination of S32, when it is determined that the first compressor 25 is operating at the lowest frequency (in the case of YES), the control unit 40 performs control to operate with the second compressor 27 (S15). In other words, the air conditioning system 1 is controlled in an operation at a low load. At this time, heat exchange is performed in the second evaporator 26, and the operating frequency of the second compressor 27 rises to the maximum frequency. Thereafter, the operating frequency of the second compressor 27 is controlled based on the temperature difference between the measured value of the blow-out temperature sensor 34 and the set value. Thereafter, the process returns to S11 again, and the above-described processing is repeatedly executed.

  In the determination of S31, when it is determined that the blowing temperature difference is greater than or equal to the predetermined threshold (in the case of YES), or in the determination of S32, it is determined that the first compressor 25 is operating at the minimum frequency or higher. In the case of NO (in the case of NO), the control unit 40 executes control for operating the first compressor 25 and the second compressor 27 (S14). At this time, heat exchange is performed in the first evaporator 24, and the rotation speeds of the first compressor 25 and the second compressor 27 are reduced. Thereafter, the process returns to S11 again, and the above-described processing is repeatedly executed.

  As in the above-described embodiment, it is determined that the blowing temperature difference, which is the difference between the measured value of the temperature of the blowing air measured by the blowing temperature sensor 34 and a predetermined set value, is less than a predetermined threshold value at a low load. By using the determination material for determining whether or not to perform control, the amount of calculation performed by the calculation unit 41 of the control unit 40 when performing the determination is reduced as compared with a determination method using estimation of required cooling capacity and power consumption. be able to. Further, whether or not the low load control is performed is determined based on the fact that the flow rate of the refrigerant discharged from the first compressor 25 is the lowest flow rate, in other words, the operating frequency of the first compressor 25 is the lowest frequency. By doing so, the air conditioning system 1 can be stably operated. That is, the start and stop of the first compressor 25 can be suppressed, and the air conditioning system 1 can be operated stably.

  In the above-described embodiment, if it is determined that the temperature of the indoor air blown from the indoor unit 20 has changed in the process of S11, is the blowout temperature difference equal to or greater than a predetermined threshold value in the subsequent process of S31? If it is determined that the temperature of the indoor air sucked into the indoor unit 20 has changed as shown in FIG. 13 instead of the difference in the blowing temperature (in the case of YES in S11a), the suction temperature It may be determined whether the difference is greater than or equal to a predetermined threshold (S31a). Here, the suction temperature difference is a difference between the temperature of the suction air sucked into the indoor unit 20 and a set value stored in advance in the storage unit 42.

  In all the above embodiments, the suction side pressure and the discharge side pressure are measured by measuring the suction side and discharge side pressures of the first compressor 25 and the second compressor 27 by applying the configuration shown in FIG. Control may be performed so that the pressure ratio, which is a ratio to the pressure, is equal to or higher than a predetermined minimum allowable pressure ratio (for example, 1.2).

  That is, the measured values of the suction side pressure and the discharge side pressure of the first compressor 25 are input to the control unit 40 from the pressure sensor 25N arranged on the suction side of the first compressor 25 and the pressure sensor 25T on the discharge side, respectively. It is comprised so that. The measured values of the suction side pressure and the discharge side pressure of the second compressor 27 are input to the control unit 40 from the pressure sensor 27N arranged on the suction side of the second compressor 27 and the pressure sensor 27T on the discharge side, respectively. It is comprised so that. Further, the control unit 40 is configured to receive control signals for controlling the respective rotation speeds to the first compressor 25 and the second compressor 27.

  When the control unit 40 determines that the pressure ratio of the first compressor 25 or the second compressor 27 is equal to or lower than the minimum allowable pressure ratio when the second compressor 27 is operated to realize the injection cycle. Alternatively, the operation of the second compressor 27 may be stopped and only the first compressor 25 may be operated. In this case, the injection cycle is not realized.

  By doing in this way, the pressure ratio in the 1st compressor 25 and the 2nd compressor 27 can be kept larger than a predetermined pressure ratio. As a result, it is possible to suppress the first compressor 25 and the second compressor 27 from repeatedly starting and stopping and to operate both stably.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the description is applied to an example in which the air-conditioning system 1 is provided with a vapor compression cycle using a fluorocarbon refrigerant or the like. A system or an air conditioning system using carbon dioxide as a refrigerant can be applied.

  Furthermore, in the above-described embodiment, the electronic device constituting the ICT device has been described as applied to an example of cooling via room air, but an example of cooling via another medium such as a heat sink instead of room air is described. It can be applied to.

  DESCRIPTION OF SYMBOLS 1 ... Air conditioning system (refrigerator), 11 ... Condenser (high pressure heat exchanger), 21 ... 1st expansion valve (1st pressure reduction part), 22 ... Gas-liquid separator, 23 ... 2nd expansion valve (2nd pressure reduction) Part), 24 ... first evaporator (first low pressure heat exchanger), 25 ... first compressor (first compression part), 26 ... second evaporator (second low pressure heat exchanger), 27 ... second Compressor (second compression unit), 28 ... first control valve (selection unit), 29 ... second control valve (selection unit), 40 ... control unit

Claims (8)

In the refrigeration system that moves the heat on the low temperature side to the high temperature side,
A high-pressure heat exchanger that cools the high-pressure refrigerant;
A first decompression unit that decompresses the high-pressure refrigerant cooled in the high-pressure heat exchanger;
A gas-liquid separator that separates the low-pressure refrigerant decompressed by the first decompression unit into a gaseous refrigerant and a refrigerant liquid;
A second decompression unit for further decompressing the liquid refrigerant separated by the gas-liquid separator;
A first low-pressure heat exchanger that evaporates the refrigerant decompressed in the second decompression unit;
A first compression section that compresses refrigerant discharged from the first low-pressure heat exchanger and discharges the refrigerant toward the high-pressure heat exchanger;
A second low-pressure heat exchanger for evaporating the low-pressure refrigerant decompressed by the first decompression unit;
The refrigerant flowing out from the second low-pressure heat exchanger and the gas refrigerant separated by the gas-liquid separator are compressed and discharged between the first compression section and the high-pressure heat exchanger. Two compression sections;
A selection unit that selects a destination of the low-pressure refrigerant decompressed by the first decompression unit from the gas-liquid separator and the second low-pressure heat exchanger;
Control of operation stop of the first compression unit and the second compression unit, and control of an inflow destination of the low-pressure refrigerant by the selection unit, and stops the first compression unit and the first A control unit that operates two compression units, and performs at least low-load control by the selection unit with the low-pressure refrigerant flowing into the second low-pressure heat exchanger;
Is provided with a refrigerator.   The refrigerator according to claim 1, wherein the second compression unit has a smaller compression capacity of the refrigerant than the first compression unit. The controller is
Difference in air temperature before and after heat exchange in the heat exchanger performing heat exchange among the first low pressure heat exchanger and the second low pressure heat exchanger, and heat exchange by the first low pressure heat exchanger The heat exchange is performed by the first heat exchanger or the second heat exchanger when the required cooling capacity based on the air flow rate and the flow rate of the refrigerant discharged from the first compression unit is the minimum flow rate. The first air temperature after
The first air temperature after the heat exchange is compared with a predetermined air temperature, and when it is determined that the first air temperature after the heat exchange is equal to or lower than the predetermined air temperature, the low load control is executed. The refrigerator according to claim 1 or 2, characterized by the above. The controller is
Difference in air temperature before and after heat exchange in the heat exchanger performing heat exchange among the first low pressure heat exchanger and the second low pressure heat exchanger, and heat exchange by the first low pressure heat exchanger The heat exchange is performed by the first heat exchanger or the second heat exchanger when the required cooling capacity based on the air flow rate and the flow rate of the refrigerant discharged from the second compression unit is the maximum flow rate. The second air temperature after
When comparing the second air temperature after the heat exchange and a predetermined air temperature, and determining that the second air temperature after the heat exchange is equal to or lower than the predetermined air temperature,
At least the power consumption when operating the first compression unit is compared with the power consumption when only the second compression unit is operated, and it is determined that the power consumption when only the second operation unit is operated is small If it is, the refrigerator according to claim 1 or 2, wherein the low load control is executed. The controller is
When the second air temperature after the heat exchange and a predetermined air temperature are compared, and it is determined that the second air temperature after the heat exchange is equal to or lower than the predetermined air temperature, and at least when the first compression unit is operated Before comparing the power consumption when operating only the second compression unit,
Heat required for the first heat exchanger or the second heat exchanger when the required cooling capacity based on the difference in air temperature and the flow rate of the air and the flow rate of the refrigerant discharged from the first compression unit is the minimum flow rate. Finding the first air temperature after being exchanged, comparing the first air temperature after the heat exchange and the predetermined air temperature,
When it is determined that the first air temperature after the heat exchange is equal to or lower than the predetermined air temperature, the power consumption of the first compression unit and the power consumption of the second compression unit are not determined, 5. The refrigerator according to claim 4, wherein the low load control is executed. The controller is
A measured value of the air temperature before or after heat exchange in the heat exchanger performing heat exchange among the first low-pressure heat exchanger and the second low-pressure heat exchanger, and a predetermined value. When it is determined that the temperature difference that is the difference between the set value of the air temperature is less than a predetermined threshold and the flow rate of the refrigerant discharged from the first compression unit is the minimum flow rate, Control is performed, The refrigerator of Claim 1 or 2 characterized by the above-mentioned. The controller is
Before obtaining at least the required cooling capacity, the air temperature before heat exchange in the heat exchanger performing heat exchange among the first low pressure heat exchanger and the second low pressure heat exchanger, or heat exchange Compare the measured value of the air temperature after being set to the preset value of the air temperature,
The at least required cooling capacity is obtained after it is determined that the measured value is lower than the set value and the difference between the measured value and the set value is equal to or greater than a predetermined threshold value. The refrigerator according to any one of the above. The controller is
When it is determined that the pressure ratio, which is the ratio between the suction side pressure and the discharge side pressure of the first compression unit and the second compression unit, is equal to or less than a predetermined pressure ratio, the operation of the second compression unit is performed. Control which stops is performed, The refrigerator of any one of Claim 1 to 7 characterized by the above-mentioned.

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