Refrigeration Cycle Device

The present disclosure relates to a refrigeration cycle device.

Patent Literature 1 discloses a refrigeration cycle device that uses refrigerant that is thermochemically unstable. In this refrigeration cycle device, when the temperature of the working medium discharged from a compressor has transient transition to a region where the temperature of the working medium discharged from the compressor is a predetermined value or higher, the temperature of the working medium discharged from the compressor is decreased by reducing the driving speed of the compressor.

The present disclosure provides a refrigeration cycle device that can suppress a disproportionation reaction of a working medium without impairing comfort for users.

The content of Japanese Patent Application No. 2022-089807 filed on Jun. 1, 2022 is incorporated herein in its entirety.

A refrigeration cycle device according to the present disclosure is a refrigeration cycle device including: an outdoor unit including a compressor; and a plurality of indoor units each including an expansion valve, wherein a working medium containing an ethylene-based fluoroolefin is used as refrigerant, the refrigeration cycle device includes a control unit, and when some indoor units of the plurality of indoor units are in an operating state, and when a discharge temperature from the compressor is a predetermined temperature or higher, the control unit opens the expansion valve of at least one of the indoor units in an operation stop state.

The refrigeration cycle device according to the present disclosure can suppress a disproportionation reaction of a working medium without impairing comfort for users.

At the time when inventors arrived at the present disclosure, a refrigeration cycle device technique is required to use, as a working medium, refrigerant with a low global warming potential (GWP), such refrigerant being less likely to contribute to climate change. Therefore, in the art, there is a problem that refrigerant with a low GWP has high reactivity, thus being unstable. In view of the above, a technique has been proposed that makes unstable refrigerant stable for use by decreasing the temperature of the working medium by reducing the driving speed of the compressor. Under such circumstances, the inventors found the problem that a reduction in driving speed of the compressor affects operation performance of indoor units in an operating state, thus impairing comfort for users. To solve this problem, the inventors have arrived at the subject matter of the present disclosure.

The present disclosure provides a refrigeration cycle device that can suppress a disproportionation reaction of a working medium without impairing comfort for users.

Hereinafter, an embodiment will be described in detail with reference to drawings. However, detailed description beyond that which is necessary may be omitted. For example, the detailed description of an already well-known matter, or repeated description of substantially the same configuration may be omitted.

Attached drawings and the description made hereinafter are provided to allow those skilled in the art to sufficiently understand the present disclosure, and are not intended to limit the subject matter described in the Claims.

is a diagram schematically showing the overall configurations of refrigeration cycle devicesaccording to an embodiment 1. Each refrigeration cycle deviceincludes indoor unitsand an outdoor unit. Each indoor unitis a device disposed in the room of a building structure, such as an office building or a house, or a mobile body, such as a ship, and performs air conditioning to an indoor space. The outdoor unitis a device mainly installed outdoors, and supplies a working medium to the indoor unitsthrough a gas pipeand a liquid pipe.

In the present embodiment, the refrigeration cycle deviceis formed by connecting four indoor unitsto one outdoor unit. The refrigeration cycle deviceincludes, in the rooms, manipulation units not shown in the drawing and corresponding to the respective indoor units, and the user sets, via the manipulation units, set temperatures or the like for the air conditioning operation performed by the corresponding indoor units. Hereinafter, the air conditioning operation including a cooling operation and a heating operation of the indoor unitis simply referred to as “operation”. In the present disclosure, the number of indoor unitsforming one refrigeration cycle deviceis not limited to four. Althoughshows the configuration in which three refrigeration cycle devicesindividually perform air conditioning for the first floor F, the second floor F, and the third floor Fof a building structure B, hereinafter, the description will be made for one refrigeration cycle devicefor the sake of convenience of description.

The refrigeration cycle deviceuses, in a refrigeration cycle circuit, a working medium containing an ethylene-based fluoroolefin. Many of ethylene-based fluoroolefins have the characteristic of having a low GWP. In contrast, it is known that an ethylene-based fluoroolefin causes a disproportionation reaction when exposed to a discharge phenomenon under high temperature and high pressure. The occurrence of a disproportionation reaction may cause a rapid rise in pressure in the refrigeration cycle circuit. The detail of the working medium will be described later.

is a diagram of the refrigeration cycle of the refrigeration cycle device. As shown in, the four indoor unitsare connected in parallel to the outdoor unitthrough the gas pipeand the liquid pipe. Each indoor unitincludes an indoor heat exchanger, an indoor fan, and an indoor expansion valve. The indoor heat exchangeris, for example, a fin tube heat exchanger, and causes a working medium flowing therethrough to exchange heat with outside air. The indoor fanis, for example, a centrifugal fan, is connected to the output shaft of an indoor fan motor, being an electronically controllable motor, and rotates with the drive of the indoor fan motorThe indoor fansuctions indoor air into the indoor unitwith the rotation thereof, and causes the indoor air to be blown out to the room through the indoor heat exchanger. The indoor expansion valve (expansion valve)is a valve in which opening/closing and an opening degree can be changed by electronic control. The indoor expansion valveallows a working medium to flow therethrough when opened, and indoor expansion valvecuts off the flow of the working medium when closed. Changes in the opening degree of the indoor expansion valvechange the flow rate of a working medium flowing through the corresponding indoor heat exchanger, and change the magnitude of a reduction in pressure, by the indoor expansion valve, of the working medium.

The outdoor unitincludes a compressor, a four-way valve, an outdoor heat exchanger, an outdoor fan, and an outdoor expansion valve. The compressoris, for example, a scroll compressor, and suctions, compresses, and then discharges a gas working medium. A working medium temperature sensoris attached in the vicinity of the discharge port of the compressor. The working medium temperature sensormeasures a discharge temperature T, which is the temperature of a working medium discharged from the compressor. The four-way valveis a device that communicates with the discharge side of the compressor, the suction side of the compressor, the outdoor heat exchanger, and the gas pipe, and can switch the flow passage for the working medium by electronic control. By switching the flow passage for the working medium by the four-way valve, whether the indoor heat exchangerserves as an evaporator or a condenser is switched. Consequently, whether the indoor unitperforms the cooling operation or the heating operation is switched.

The outdoor heat exchangeris, for example, a fin tube heat exchanger, and causes a working medium flowing therethrough to exchange heat with outside air. The outdoor fanis, for example, an axial-flow fan, is connected to the output shaft of an outdoor fan motor, being an electronically controllable motor, and rotates with the drive of the outdoor fan motorThe outdoor fansuctions outside air into the outdoor unitwith the rotation thereof, and causes the suctioned outside air to be blown out to the outside the outdoor unitthrough the outdoor heat exchanger. The outdoor expansion valveis a valve in which the opening degree can be changed by electronic control, for example, and the outdoor expansion valvereduces the pressure of a working medium passing through the outdoor expansion valve.

The gas pipeis a refrigerant pipe that causes the four-way valveto communicate with the indoor expansion valvesincluded in the respective indoor units. A working medium flowing through the gas pipeis mainly in a gas state. The liquid pipeis a refrigerant pipe that causes the outdoor expansion valveto communicate with the indoor heat exchangersincluded in the respective indoor units. A working medium flowing through the liquid pipeis mainly in a liquid state.

is a block diagram showing the configuration of the control system of the refrigeration cycle device. The four indoor unitshave the same configuration and hence, in, the detailed configuration of only one indoor unitis described, and the detailed configuration of three indoor unitsis omitted.

The indoor unitincludes a room temperature sensor, an indoor communication unit, and a motion sensor. The room temperature sensoris a sensor that measures room temperature at a predetermined sampling rate. The indoor communication unitis communication hardware corresponding to predetermined communication standards, such as a connector or a communication circuit, and communicates with the outdoor unitthrough a control wiring. The motion sensoris, for example, an infrared sensor, and senses a person present in the space in which the indoor unitis installed.

The outdoor unitincludes an outdoor communication unitand a control unit. The outdoor communication unitis communication hardware corresponding to predetermined communication standards, such as a connector or a communication circuit, and communicates with the indoor communication unitthrough a control wiring.

The control unitcontrols actions of the respective components of the refrigeration cycle device. The control unitincludes an outdoor unit memory, an outdoor unit processor, and an outdoor unit interface.

The outdoor unit memoryis a memory that stores programs and data. The outdoor unit memorystores various control programs, and data to be processed by the outdoor unit processor. The outdoor unit memoryhas a non-volatile storage area. The outdoor unit memorymay also has a volatile storage area to form a work area for the outdoor unit processor.

The outdoor unit processoris a processor, such as a CPU or an MPU. When the outdoor unit processorreads and executes the control program stored in the outdoor unit memory, the outdoor unit processorserves as an equipment control unitand a determination unit

The outdoor unit interfaceis an interface that includes communication hardware corresponding to predetermined communication standards, such as a connector or a communication circuit. The outdoor unit interfacecommunicates with the outdoor communication unit, the compressor, the four-way valve, the outdoor fan motorthe outdoor expansion valve, and the working medium temperature sensor.

The equipment control unitreceives, as a signal, manipulation performed by the user on the manipulation unit not shown in the drawing and provided in the room, and performs the operation by controlling respective pieces of equipment of the refrigeration cycle devicein response to the received signal. The equipment control unitcontrols, via the outdoor unit interface, the respective components of the outdoor unit, such as the outdoor communication unit, the compressor, the four-way valve, the outdoor fan motorand the outdoor expansion valve. The equipment control unitalso controls, via the outdoor communication unitand the indoor communication unit, the respective components of each indoor unit, such as the indoor fan motorand the indoor expansion valve, thus individually operating or stopping the operation of the four indoor units. The indoor unitin an operation stop state includes the indoor unitin a thermo-off operation state. A thermo-off operation is an operation performed when the determination unitdescribed later determines that room temperature data measured by the room temperature sensormatches the set temperature set by the user. When the indoor unitin a normal operation state shifts to the thermo-off operation state, the indoor expansion valveof the indoor unitis closed to prevent room temperature from being changed more than necessary.

The determination unitreceives data on the measured discharge temperature T from the working medium temperature sensor. The determination unitalso receives, via the outdoor communication unitand the indoor communication unit, room temperature data measured by the room temperature sensor, and data transmitted from the motion sensor. As will be described later, the determination unitperforms various determinations based on various received data, and then causes, based on the results of the determinations, the equipment control unitto change control performed on the respective pieces of equipment.

Refrigerant used in the refrigeration cycle deviceis a working medium containing an ethylene-based fluoroolefin. Ethylene-based fluoroolefins include, for example, any one or more of 1, 1, 2-trifluoroethylene (HFO1123), trans-1, 2-difluoroethylene (HF01132(E)), cis-1, 2-difluoroethylene (HFO-1132(Z)), 1, 1-difluoroethylene (HFO-1132a), tetrafluoroethylene (CF2=CF2, HFO1114), and monofluoroethylene (HFO-1141).

The above-mentioned working medium may contain two or more refrigerant components. That is, the above-mentioned working medium may contain an ethylene-based fluoroolefin selected from the above-mentioned examples (for example, 1, 1, 2-trifluoroethylene), and a second refrigerant component. Examples of the second refrigerant component include one or more refrigerants selected from hydrofluorocarbons (HFC), hydrofluoroolefins (HFO), saturated hydrocarbons, carbon dioxide, and other refrigerants. Examples of hydrofluorocarbons include difluoromethane, difluoroethane, trifluoroethane, tetrafluoroethane, pentafluoroethane, pentafluoropropane, hexafluoropropane, heptafluoropropane, pentafluorobutane, and heptafluorocyclopentane. Examples of hydrofluoroolefins include monofluoropropene, trifluoropropene, tetrafluoropropene, pentafluoropropene, and hexafluorobutene. Although examples of saturated hydrocarbons include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2, 2-dimethylpropane), and methylcyclobutane, other hydrocarbons may be used. The second refrigerant component may contain a plurality of components. That is, the second refrigerant component may contain two or more refrigerant components selected from hydrofluorocarbons, hydrofluoroolefins, saturated hydrocarbons, carbon dioxide, and other refrigerants.

The working medium used as refrigerant in the refrigeration cycle devicemay contain a disproportionation inhibiting agent in addition to the refrigerant component. An example of the disproportionation inhibiting agent includes a saturated hydrocarbon. The working medium may contain a disproportionation inhibiting agent made of one or a plurality of components. Although examples of saturated hydrocarbons used as the disproportionation inhibiting agent include ethane, n-propane, cyclopropane, n-butane, cyclobutane, isobutane (2-methylpropane), methylcyclopropane, n-pentane, isopentane (2-methylbutane), neopentane (2, 2-dimethylpropane), and methylcyclobutane, other saturated hydrocarbons may be used. An example of a particularly preferable disproportionation inhibiting agent includes n-propane.

The disproportionation inhibiting agent may be, for example, a haloalkane with the number of carbons of either one or two. Haloalkanes with the number of carbons of one, that is, halomethanes, may be used as the disproportionation inhibiting agent. Although examples of halomethanes include (mono) iodomethane (CH3I), diiodomethane (CH2I2), dibromomethane (CH2Br2), bromomethane (CH3Br), dichloromethane (CH2Cl2), chloroiodomethane (CH2ClI), dibromochloromethane (CHBr2Cl), tetraiodomethane (CI4), carbon tetrabromide (CBr4), bromotrichloromethane (CBrCl3), dibromodichloromethane (CBr2Cl2), tribromofluoromethane (CBr3F), fluorodiiodomethane (CHFI2), difluoroiodomethane (CHF2I), difluorodiiodomethane (CF2I2), dibromodifluoromethane (CBr2F2), and trifluoroiodomethane (CF3I), other halomethanes may be used. Haloalkanes with the number of carbons of two, that is, haloethanes, may be used as the disproportionation inhibiting agent. Examples of haloethanes include 1, 1, 1-trifluoro-2-iodoethane (CF3CH2I), monoiodoethane (CH3CH2I), monobromoethane (CH3CH2Br), and 1, 1, 1-triiodoethane (CH3CI3).

The working medium may contain a plurality of disproportionation inhibiting agents selected from the above-mentioned saturated hydrocarbons and the above-mentioned haloalkanes. The working medium may contain one kind of saturated hydrocarbon, or may be a working medium containing two or more kinds of saturated hydrocarbons. The working medium may contain one kind of haloalkane, or may be a working medium containing two or more kinds of haloalkanes.

A preferred example of the working medium includes a mixture containing 1, 1, 2-trifluoroethylene and n-propane. This working medium may contain the second refrigerant component described above, or may contain other components.

The above-mentioned each working medium may contain unavoidable impurities. Examples of the unavoidable impurities include various additives, such as a stabilizing agent added for the purpose of stabilization during transportation or during storage, the residue or by-product of a synthetic raw material of the refrigerant component, and substances mixed for other reasons.

The mass ratio between 1, 1, 2-trifluoroethylene and n-propane contained in the working medium may be suitably changed. The capacity of the refrigeration cycle correlates to the mass ratio of refrigerant component contained in the working medium. Accordingly, to maintain the capacity of the refrigeration cycle, it is desirable to have a configuration in which n-propane, being the disproportionation inhibiting agent, is contained in the working medium at 40 mass % or less.

The action and the manner of operation of the refrigeration cycle devicehaving the above-mentioned configuration will be described hereinafter.

A predetermined temperature Tused in the description made hereinafter is determined according to, for example, heat resistance of an insulating paper inserted between a magnet wire and an electromagnetic steel sheet in the stator of a motor forming the compressor, the magnet wire and the electromagnetic steel sheet generating a magnetic field by energization. For example, when a heat resistance class, specified by JIS C 4003, of an insulating paper is a heat resistance class B, a heat resistance temperature is 130° C. When the insulating paper is placed under a temperature condition higher than this heat resistance temperature, insulation between the magnet wire and the electromagnetic steel sheet is broken, thus increasing a possibility of occurrence of a discharge phenomenon that may cause a disproportionation reaction. The temperature condition of the insulating paper is substantially equal to the discharge temperature T and hence, the refrigeration cycle devicechanges the action thereof depending on whether the measured value of the discharge temperature T is the predetermined temperature Tor higher.

In the present embodiment, an insulating paper in a heat resistance class E specified by JIS C 4003 is used, and the heat resistance temperature of this insulating paper is 120° C. The predetermined temperature Tl is 115° C. obtained by giving a margin for safety of approximately 5K to this heat resistance temperature. In the case in which the temperature of the working medium is 150° C. or higher, a risk of occurrence of a disproportionation reaction increases irrespective of the heat resistance temperature of the insulating paper. Therefore, even in the case in which an insulating paper having a heat resistance temperature of 150° C. or higher is used, the predetermined temperature Tis set to a temperature obtained by giving a margin for safety to 150° C. That is, the predetermined temperature Tis set based on whichever is lower of a temperature having a high risk of occurrence of a discharge phenomenon or a temperature having a high risk of occurrence of a disproportionation reaction due to a high temperature itself.

is a flowchart of the refrigeration cycle device, and shows actions of the refrigeration cycle device. Hereinafter, the description will be made by taking, as an example, the case in which, of the four indoor unitsof the refrigeration cycle device, a plurality of indoor unitsare in an operating state at the start point of the flowchart in.

In this state, the equipment control unitactivates the compressorto cause a working medium to circulate through the refrigeration cycle circuit. In addition, the equipment control unitcloses the indoor expansion valvesprovided in indoor unitsin an operation stop state, and opens the indoor expansion valvesprovided in indoor unitsin an operating state. Consequently, the working medium that circulates with the drive of the compressordoes not flow into the indoor unitsin an operation stop state, but flows only to the indoor unitsin an operating state.

The equipment control unitalso controls the indoor expansion valvessuch that each indoor expansion valveprovided in the indoor unitin an operating state has a larger opening degree substantially in proportion to required condensing capacity or required evaporating capacity for each indoor unit. A larger difference between the set temperature and room temperature, and a larger number of revolutions of the indoor fanmainly require each indoor unitto have a larger condensing capacity and a larger evaporating capacity.

In addition to the above, the equipment control unitcauses, of the indoor unitsin an operating state, the indoor unitshaving higher pressure losses dP to have a larger opening degree of the indoor expansion valveof each indoor unit, the pressure loss dP being generated in the working medium in the area from the compressorto each indoor unit. Consequently, the indoor unitshaving higher pressure losses dP have a larger opening degree of the indoor expansion valveper condensing capacity or evaporating capacity of each indoor unit. The pressure loss dP mainly depends on the installation state of the refrigeration cycle device, such as the length of the refrigerant pipe from the compressorto the indoor unit, the diameter of the refrigerant pipe, the number and curvature of bent portions of the refrigerant pipe, and the height of the indoor unitrelative to the compressor.

The equipment control unitmay control the indoor expansion valvesassuming that, for example, an indoor unithaving a longer length of the refrigerant pipe between the outdoor unitand the indoor unitis the indoor unithaving a higher pressure loss dP. A configuration may be adopted in which the order of the lengths of the refrigerant pipes between the outdoor unitand the respective indoor unitsis determined by the worker at the time of installing the refrigeration cycle device, for example, and the order based on the determination is stored in the outdoor unit memory. In the same manner, information on the orders or the like of the diameters of the refrigerant pipes, the number and curvatures of bent portions of the refrigerant pipes, and the heights of the indoor units, and the combination of the above may be used instead of the above-mentioned information on the order of the lengths of the refrigerant pipes. Alternatively, a configuration may be adopted in which the pressure of the working medium in the refrigerant pipe in the vicinity of each indoor unitin an operating state is measured, and the equipment control unitcontrols the indoor expansion valvesassuming that an indoor unithaving a smaller measured value of the pressure of the working medium in the refrigerant pipe is the indoor unithaving a higher pressure loss dP. A configuration may be adopted in which the pressure of the working medium in the refrigerant pipe in the vicinity of each indoor unitis measured by, for example, a pressure sensor not shown in the drawing and connected to the indoor unit, and is transmitted to the equipment control unitvia the indoor communication unitand the outdoor communication unit. In this case, the equipment control unitcan control the indoor expansion valvesby taking into account the pressure loss dP, with not only factors determined at the time of installing the refrigeration cycle device, but also factors, such as an air conditioning load, for example.

During a period in which the refrigeration cycle deviceperforms a normal operation as described above, the working medium temperature sensorcontinues to measure, at the predetermined sampling rate, the discharge temperature T of the working medium discharged from the compressor, and then transmits data on the measured value to the determination unitThe determination unitdetermines whether the received measured value of the discharge temperature T is the predetermined temperature Tor higher (step S). When it is determined that the measured value of the discharge temperature T is less than the predetermined temperature T(step S: NO), the refrigeration cycle devicecontinues the normal operation. In contrast, when it is determined that the measured value of the discharge temperature T is the predetermined temperature Tor higher (step S: YES), the process shifts to step S.

In step S, the equipment control unitcauses, of the indoor unitsin an operating state, the indoor units having lower pressure losses dP from the compressorto have a larger opening degree of the indoor expansion valve. Consequently, in the refrigeration cycle circuit, the working medium quickly moves from the high pressure side to the low pressure side. Therefore, the pressure on the high pressure side rapidly decreases in the refrigeration cycle circuit.

In step S, the determination unitdetermines whether all of four indoor unitsof the refrigeration cycle deviceare in an operating state. When the determination unitdetermines that all of the indoor unitsare in an operating state (step S: YES), the process shifts to step S. When the determination unitdetermines that not all of the indoor unitsof the refrigeration cycle deviceare in an operating state (step S: NO), that is, some of the indoor unitsare in an operating state, but other indoor unitsare not in an operating state, the process shifts to step S.

In step S, the determination unitdetermines whether the indoor unitthat is in an operating state is newly brought into an operation stop state. Examples of the case in which the indoor unitis newly brought into an operation stop state include the case in which the indoor unitin an operating state is brought into an operation stop state by the manipulation performed by the user, and the case in which the indoor unitin an operating state is shifted to the thermo-off operation. When the determination unitdetermines that the indoor unitin an operating state is newly brought into an operation stop state (step S: YES), the process shifts to step S. The determination unitrepeats the determination in step Suntil the indoor unitis newly brought into an operation stop state.

In step S, the equipment control unitopens the indoor expansion valveof at least one of the indoor unitsin an operation stop state. Consequently, a pressure on the high pressure side of the refrigeration cycle circuit can be easily released to the low pressure side through the indoor expansion valvethat is opened.

The opening degree of the indoor expansion valvethat is opened in step Smay be an opening degree smaller than the minimum opening degree, being the minimum value of the opening degree for the indoor unitin an operating state. Hereinafter, such an opening degree is referred to as “extremely small opening degree”. The range of the opening degree adopted during the operation of the indoor unitis determined by, for example, the relationship between the opening degree of the indoor expansion valveand a Cv value specified by JIS B 0100. To be more specific, the range of the opening degree of the indoor expansion valveadopted during the operation of the indoor unitis a region where a Cv curve plotted with the opening degree of the indoor expansion valveon an axis and the Cv value on the other axis forms a substantially straight line and, in the present embodiment, such a region is where the opening degree is approximately 5% or more. The minimum opening degree is the minimum opening degree in this region and hence, the minimum opening degree is approximately 5%. In the case of the present embodiment, in the region where the opening degree is approximately 5% or less, the Cv value rapidly changes relative to the change in the opening degree of the indoor expansion valve, the Cv value indicating flowability of a fluid. Therefore, the region where the opening degree is approximately 5% or less is not suitable for control of the flow rate of the working medium. Accordingly, in the present embodiment, when the indoor unitis in an operating state, the equipment control unitperforms control in such a way as to prevent the opening degree of the corresponding indoor expansion valvefrom becoming approximately 5% or less.

In step S, a configuration may be adopted in which, of the indoor expansion valvesof the indoor unitsin an operation stop state, the number and the opening degree of indoor expansion valvesthat are opened are set according to the discharge temperature T. For example, a configuration may be adopted in which the total of the opening degrees of the indoor expansion valvesthat are opened in step Sis controlled in such a way as to correlate to a temperature range by which the discharge temperature T exceeds the predetermined temperature T. With such a configuration, when the discharge temperature T is a high temperature, a pressure on the high pressure side in the refrigeration cycle circuit can be released more easily and hence, it is possible to effectively suppress occurrence of a disproportionation reaction. However, from the viewpoint of energy efficiency, it is preferable to perform a control such that the total of the opening degrees of the indoor expansion valvesof the indoor unitsthat are brought into an operation stop state is equal to or less than the total of the opening degrees of the indoor expansion valvesof the indoor unitsin an operating state.