Patent Grant
10036562
The present invention relates to an air-conditioning apparatus.
In recent years, in terms of global environmental protection, cases where heat-pump air-conditioning apparatuses which use air as a heat source are introduced even in cold regions, instead of known boiler-type heating devices which burn fossil fuels to perform heating, have increased. With heat-pump air-conditioning apparatuses, heating is able to be performed more efficiently by the amount of heat supplied from air, in addition to electric input to a compressor. In contrast, however, when the temperature of outside air is low, frost is deposited on an outdoor heat exchanger serving as an evaporator, it is therefore necessary to perform defrosting to melt frost deposited on the outdoor heat exchanger. As a method for performing defrosting, there is a method for reversing a refrigeration cycle. With this method, however, heating of a room is stopped during defrosting. Therefore, there is a problem of impairing comfort.
As a method for being able to perform heating even during defrosting, methods have been developed (see, for example, Patent Literature 1, Patent Literature 2, and Patent Literature 3), in which an outdoor heat exchanger is divided, with part of the outdoor heat exchangers performing defrosting, while the other heat exchangers being caused to operate as evaporators, which receive heat from air and thus perform heating.
In Patent Literature 1, in the case where an outdoor heat exchanger is divided into plural parallel heat exchangers and defrosting of one parallel heat exchanger is performed, by closing a flow rate control device which is installed near the other parallel heat exchanger and opening a flow rate control device at a bypass pipe which causes a refrigerant to take a detour to the inlet of the parallel heat exchanger from a discharge pipe of a compressor, part of a high-temperature refrigerant that has been discharged from the compressor is caused to flow into the parallel heat exchanger directly. Then, after defrosting of the one parallel heat exchanger is completed, defrosting of the other parallel heat exchanger is performed. At this time, defrosting of the other parallel heat exchanger is performed in a state where the pressure of a refrigerant inside the other parallel heat exchanger is substantially the same as the suction pressure of the compressor (low-pressure defrosting).
In Patent Literature 2, plural outdoor units and at least one or more indoor units are provided. The direction of connection of a four-way valve in only an outdoor unit that includes an outdoor heat exchanger subjected to defrosting is reversed relative to that in a heating operation, so that a refrigerant that has been discharged from a compressor is caused to flow into the outdoor heat exchanger directly. At this time, defrosting is performed in a state where the pressure of a refrigerant in the heat exchanger subjected to defrosting is substantially the same as the discharge pressure (high-pressure defrosting).
In Patent Literature 3, an outdoor heat exchanger is divided into plural parallel heat exchangers. By causing part of a high-temperature refrigerant that has been discharged from a compressor to flow into the parallel heat exchangers alternately, and defrosting of the parallel heat exchangers is performed alternately. Accordingly, continuous heating can be performed without reversing a refrigeration cycle. Further, in Patent Literature 3, medium-pressure defrosting is proposed in which defrosting is performed in a state where the pressure of a refrigerant in a parallel heat exchanger subjected to defrosting is not the same as the discharge pressure or the suction pressure but is slightly higher than that at 0 degrees Centigrade when converted into a saturation temperature and the refrigerant is returned to an injection part of an injection compressor.
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2009-085484 (Page 11, FIG. 3)
Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2007-271094 (Page 8, FIG. 2)
Patent Literature 3: International Publication No. WO 2012/014345 (Page 9, FIG. 1)
In low-pressure defrosting such as Patent Literature 1, since an evaporator (a parallel heat exchanger which is not being subjected to defrosting) operating in the same pressure zone as that of a parallel heat exchanger which is being subjected to defrosting receives heat from outside air, the evaporating temperature of a refrigerant is lower than the outside air temperature. Therefore, even at the parallel heat exchanger that is being subjected to defrosting, the saturation temperature is at or below 0 degrees Centigrade, and condensed latent heat of the refrigerant cannot be used for melting frost (0 degrees Centigrade). Thus, defrosting is performed inefficiently.
In contrast, in low-pressure defrosting of patent Literature 2, the subcooling (degree of subcooling) of a refrigerant at the outlet of an outdoor heat exchanger for which defrosting is completed is large, and temperature distribution occurs. Therefore, high-efficient defrosting cannot be performed. Further, the amount of liquid refrigerant inside the outdoor heat exchanger increases by the large amount of subcooling. Therefore, a time may be required for movement of the liquid refrigerant.
In medium-pressure defrosting of Patent Literature 3, by controlling the saturation temperature of a refrigerant to be slightly higher (about between 0 degrees Centigrade to about 10 degrees Centigrade) than 0 degrees Centigrade, defrosting of the entire parallel heat exchanger can be performed efficiently and with less temperature variations, compared to Patent Literature 1 and Patent Literature 2, while utilizing condensed latent heat. However, in Patent Literature 3 pressures before and after a flow switching device for performing switching of connection on the compressor side of the parallel heat exchangers greatly vary among cooling, heating, and defrosting. Therefore, as the flow switching device, a solenoid valve capable of being controlled irrespective of the pressures before and after thereof is used.
However, in general, solenoid valves have a Cv value smaller than those of four-way valves, three-way valves, and the like, which are generally used for air-conditioning as flow switching valves. More specifically, while four-way valves with a maximum Cv value of up to about “17” are generally and widely distributed, commonly available solenoid valves are those with a maximum Cv value of up to about “3”. There is, therefore, a problem in that using a solenoid valve as a flow switching valve causes a large amount of pressure loss. In terms of pressure loss, it is preferable that a simple switching valve, such as a four-way valve or a three-way valve, is used, instead of using a solenoid valve as a flow switching valve.
However, because of the structure of four-way valves and three-way valves, they need to be connected so that a refrigerant flows in a single direction. That is, in order to properly operate a four-way valve or three-way valve, the pressure of one port needs to be always higher than the pressure of the other port. Therefore, in a part in which pressure inside an outdoor heat exchanger largely changes among pressure zones: high pressure in cooling; low pressure in heating; and medium pressure in defrosting, it is difficult to use a four-way valve or a three-way valve. Thus, a solenoid valve having a complicated bidirectional structure is inevitably used.
Further, solenoid valves through which a refrigerant flows in a single direction has a Cv value in a range wider than that of bidirectional solenoid valves. Therefore, improvement in pressure loss can be expected by using a unidirectional solenoid valve instead of a bidirectional solenoid valve. However, similar to the case of four-way valves and three-way valves, unidirectional solenoid valves also need to be connected so that a refrigerant flows in a single direction, and thus in actuality cannot be used.
As described above, medium-pressure defrosting in Patent Literature 3 has the advantage of being able to perform defrosting efficiently but, at the same time, has a problem that a bidirectional solenoid valve having a complicated structure needs to be used, as a flow switching valve, which causes an increase in the cost.
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an air-conditioning apparatus capable of achieving defrosting using a four-way valve or a three-way valve and a unidirectional solenoid valve having simple structures, without using a bidirectional solenoid valve having a complicated structure.
An air-conditioning apparatus according to the present invention includes a main circuit which is configured such that a compressor, a cooling/heating switching device that is connected between a discharge pipe of the compressor and a suction pipe of the compressor and that performs switching of a flow direction of a refrigerant, indoor heat exchangers, first flow rate control devices, and an outdoor heat exchanger that is divided into plural parallel heat exchangers are connected by piping; a first bypass pipe which has one end connected to the discharge pipe, and the other end divided into branch pipes which are respectively connected to first connection pipes that extend from the plural parallel heat exchangers toward the first flow rate control devices, and which supplies part of the refrigerant that has been discharged from the compressor and has then been decompressed at an expansion device to a parallel heat exchanger of the parallel heat exchangers subjected to defrosting; a second bypass pipe which has one end connected to an injection port of the compressor that communicates with a compression chamber in a process of compression, and the other end divided into branch pipes which are respectively connected to second connection pipes that extend from the respective plural parallel heat exchangers toward the compressor, and in which the refrigerant that has passed through the plural parallel heat exchangers is injected via the injection port; a first flow switching unit which performs switching of a connection mode of ends of the plural parallel heat exchangers on a side of the compressor to one of three modes: a mode in which the ends are connected to a discharge side of the compressor; a mode in which the ends are connected to a suction side of the compressor; and a mode in which the ends are connected to neither the discharge side nor the suction side of the compressor; a second flow switching unit which performs switching of a connection mode of ends of the plural parallel heat exchangers on the sides opposite to the compressor to one of a mode in which the ends are connected to the first bypass pipe and a mode in which the ends are connected to a main pipe in the main circuit; and a third flow switching unit which opens and closes a flow passage inside the second bypass pipe and connects one of the plural parallel heat exchangers to the injection port when the flow passage is opened. The first flow switching unit includes first connection switching devices that are provided at the second connection pipes and perform switching of a connection destination of the second connection pipes to one of a high-pressure pipe which branches off from the discharge pipe and a low-pressure pipe which branches off from the suction pipe, and second connection switching devices that are provided at respective pipes connecting the second connection pipes with the high-pressure pipe and that perform switching of a connection mode of the second connection pipes to one of a mode in which the second connection pipes are connected to the high-pressure pipe and a mode in which the second connection pipes are disconnected from the high-pressure pipe, when the connection destination of the second connection pipes is switched toward the high-pressure pipe by the first connection switching devices. The first connection switching devices are configured such that check valves are connected in series to third ports of high/low pressure switching devices each including a three-way valve or a four-way valve that a first port of which is connected to the high-pressure pipe and a second port of which is connected to the low-pressure pipe so that the refrigerant is allowed to flow only from sides of the second connection pipes to the high/low pressure switching devices. The second connection switching devices are switching devices which each include a unidirectional solenoid valve, or switching devices that are configured such that check valves are connected in series to third ports of three-way valves or four-way valves that first ports of which are connected to the high-pressure pipe and second ports of which are connected to the low-pressure pipe so that the refrigerant is allowed to flow only from the three-way valves or the four-way valves to the second connection pipes.
According to the present invention, an air-conditioning apparatus capable of performing high-efficiency defrosting, without stopping heating by an indoor unit, can be obtained, by not using a bidirectional solenoid valve having a complicated structure but by using a simple valve.
Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
The air-conditioning apparatus 100 includes an outdoor unit A and indoor units B and C which are connected in parallel to each other. The outdoor unit A and the indoor units B and C are connected by first extension pipes 8-1 and 8-2 and second extension pipes 9-1 and 9-2. The air-conditioning apparatus 100 also includes a controller (not illustrated). The controller controls a cooling operation, and a heating operation (normal heating operation and heating and defrosting operation) of the indoor units B and C.
As a refrigerant, a fluorocarbon refrigerant (for example, an HFC-type refrigerant, such as an R32 refrigerant, R125, or R134a, a mixture of the above refrigerants, such as R410A, R407c, or R404A) or an HFO refrigerant (for example, HFO-1234yf, HFO-1234ze(E), or HFO-1234ze(Z)) may be used. In addition, a refrigerant used for vapor-compression heat pumps, such as a CO2 refrigerant, an HC refrigerant (for example, a propane or isobutane refrigerant), an ammonia refrigerant, or a mixed refrigerant of the above-mentioned refrigerants, such as a mixed refrigerant of R32 and HFO-1234yf, may be used.
In Embodiment 1, an example in which two indoor units are connected to one outdoor unit is explained. However, only one indoor unit may be connected or two or more outdoor units may be connected in parallel. Furthermore, a refrigerant circuit configuration which achieves a cooling and heating simultaneous operation in which each unit selects cooling or heating, can be provided, by connecting three extension pipes in parallel or providing a switching valve in the indoor unit.
A configuration of a refrigerant circuit in the air-conditioning apparatus 100 will now be explained.
The refrigerant circuit of the air-conditioning apparatus 100 includes a main circuit in which a compressor 1, a cooling/heating switching device 2-1 for switching between cooling and heating, indoor heat exchangers 3-b and 3-c, first flow rate control devices 4-b and 4-c that are freely opened and closed, and an outdoor heat exchanger 5 are sequentially connected by a pipe. The main circuit further includes an accumulator 6. However, the accumulator 6 is not necessarily essential and may be omitted.
The compressor 1 is a compressor into which a medium-pressure refrigerant is able to be injected in the process of compression of a refrigerant from low pressure to high pressure.
The cooling/heating switching device 2-1 is connected between a discharge pipe 1a and a suction pipe 1b of the compressor 1 and includes, for example, a four-way valve for switching the flow direction of a refrigerant. In a heating operation, the cooling/heating switching device 2-1 is connected in the direction of solid lines in
The outdoor heat exchanger 5 is divided into plural parallel heat exchangers, namely parallel heat exchangers 5-1 and 5-2, in this configuration. The parallel heat exchangers 5-1 and 5-2 are formed by dividing the outdoor heat exchanger 5 that extends in a horizontal direction in the casing of the outdoor unit A. Although the outdoor heat exchanger 5 may be divided horizontally, horizontal division causes a refrigerant to enter the parallel heat exchangers 5-1 and 5-2 from left and right ends of the outdoor unit A, which complicates pipe connection. Thus, it is preferable that the outdoor heat exchanger 5 is divided in a vertical direction.
Outdoor air is conveyed to the parallel heat exchangers 5-1 and 5-2 by an outdoor fan 17. The outdoor fan 17 may be installed at each of the parallel heat exchangers 5-1 and 5-2. However, as illustrated in
First connection pipes 20-1 and 20-2 are connected to the parallel heat exchangers 5-1 and 5-2 on sides connected with the first flow rate control devices 4-b and 4-c. The first connection pipes 20-1 and 20-2 are connected in parallel to a main pipe extending from second flow rate control devices 7-1 and 7-2. The second flow rate control devices 7-1 and 7-2 are provided at the first connection pipes 20-1 and 20-2, respectively.
Second connection pipes 21-1 and 21-2 are connected to the parallel heat exchangers 5-1 and 5-2 on sides connected with the compressor 1. The second connection pipes 21-1 and 21-2 are connected to the compressor 1 via a first flow switching unit 110.
The first flow switching unit 110 performs switching of a connection mode of the ends of the parallel heat exchangers 5-1 and 5-2 on the side of the compressor 1, to one of three modes: a mode in which these ends are connected to the discharge side of the compressor 1, a mode in which these ends are connected to the suction side of the compressor 1, and a mode in which these ends are connected to neither the discharge side nor the suction side of the compressor 1. The details of the first flow switching unit 110 will be described later.
The refrigerant circuit also includes a first bypass pipe 22 which supplies part of a high-temperature high-pressure refrigerant for the purpose of defrosting that has been discharged from the compressor 1 to the parallel heat exchangers 5-1 and 5-2. One end of the first bypass pipe 22 is connected to the discharge pipe 1a. The other end of the first bypass pipe 22 is divided into branch pipes and the branch pipes are connected to the first connection pipes 20-1 and 20-2.
An expansion device 14 is provided at the first bypass pipe 22. Part of the high-temperature high-pressure refrigerant that has been discharged from the compressor 1 is reduced into medium pressure at the expansion device 14 and then supplied to the parallel heat exchangers 5-1 and 5-2. Unidirectional solenoid valves (hereinafter, simply referred to as solenoid valves) 12-1 and 12-2 by which a refrigerant flows in a single direction are provided at the branch pipes which branch off from the first bypass pipe 22. The arrows provided for the solenoid valves 12-1 and 12-2 in
The solenoid valves 12-1 and 12-2 and the second flow rate control devices 7-1 and 7-2 form a second flow switching unit 120 which performs switching of connection destinations of sides of the parallel heat exchangers 5-1 and 5-2 remote from the compressor 1, between the first bypass pipe 22 and the main circuit. Although the expansion device 14 may be a capillary tube illustrated in
The refrigerant circuit also includes a second bypass pipe 23 for injecting a refrigerant that has flowed out of the parallel heat exchangers 5-1 and 5-2 into the compressor 1. A downstream-side end of the second bypass pipe 23 is connected to an injection port of the compressor 1 which is communicated with a compression chamber in the process of compression. An upstream-side end of the second bypass pipe 23 is divided into branch pipes and the branch pipes are connected to the second connection pipes 21-1 and 21-2.
A third flow switching unit 130 is provided at the second bypass pipe 23. The third flow switching unit 130 opens and closes a flow passage at the second bypass pipe 23 and connects one of the parallel heat exchangers 5-1 and 5-2 to the injection port when the flow passage is opened. The third flow switching unit 130 includes unidirectional solenoid valves (hereinafter, simply referred to as solenoid valves) 12-3 and 12-4 and check valves 13-1 and 13-2, which are provided at branch pipes which branch off from the upstream side of the second bypass pipe 23.
Next, the first flow switching unit 110 will be explained.
The first flow switching unit 110 includes first connection switching devices 111-1 and 111-2 and second connection switching devices 112-1 and 112-2.
The first connection switching devices 111-1 and 111-2 are devices which switch connection destinations of the second connection pipes 21-1 and 21-2 between a high-pressure pipe 11a and a low-pressure pipe 11b. The first connection switching devices 111-1 and 111-2 are provided at the second connection pipes 21-1 and 21-2 and include four-way valves (high/low pressure switching devices) 2-2 and 2-3 for performing switching of connection between high pressure and low pressure, and check valves 11-1 and 11-2, respectively.
The four-way valves 2-2 and 2-3 each have four ports. First ports (high-pressure ports) X are connected to the high-pressure pipe 11a which branches off from the discharge pipe 1a. Second ports (low-pressure ports) Y are connected to the low-pressure pipe 11b, which branches off from the suction pipe 1b. Third ports are connected to the second connection pipes 21-1 and 21-2 via the check valves 11-1 and 11-2. The check valves 11-1 and 11-2 are connected in series with the third ports so that a refrigerant can flow only from the second connection pipes 21-1 and 21-2 to the four-way valves 2-2 and 2-3. Fourth ports are closed. With the above-mentioned connection, the first ports X are fixed at high pressure, and the second ports are fixed at low pressure.
The second connection switching devices 112-1 and 112-2 are devices that switch between a state where the second connection pipes 21-1 and 21-2 are connected to the high-pressure pipe 11a and a state where the second connection pipes 21-1 and 21-2 are disconnected from the high-pressure pipe 11a when the connection destinations of the second connection pipes 21-1 and 21-2 are switched to the high-pressure pipe 11a side by the first connection switching devices 111-1 and 111-2 (when the four-way valves 2-2 and 2-3 are switched to the dotted lines side in
With the first flow switching unit 110 configured as described above, a selection can be freely made from three options: a state where the parallel heat exchangers 5-1 and 5-2 are connected to the discharge side of the compressor 1; the parallel heat exchangers 5-1 and 5-2 are connected to the suction side of the compressor 1; and the parallel heat exchangers 5-1 and 5-2 are not connected to either side. In the case where the parallel heat exchangers 5-1 and 5-2 are connected to neither the discharge side nor the suction side of the compressor 1 by the first flow switching unit 110, the parallel heat exchangers 5-1 and 5-2 are connected to the injection port of the compressor 1 by the third flow switching unit 130.
Although the configuration in which solenoid valves 10-1 and 10-2 are used as the second connection switching devices 112-1 and 112-2 is illustrated in
The refrigerant circuit also includes a third flow rate control device 15 and an inner heat exchanger 16. The third flow rate control device 15 reduces the pressure of a refrigerant split from a refrigerant that has flowed out of the first flow rate control devices 4-b and 4-c in the main circuit.
The inner heat exchanger 16 includes a high-pressure side flow passage and a low-pressure side flow passage. The inner heat exchanger 16 exchanges heat between a refrigerant passing through the high-pressure side flow passage and a refrigerant passing through the low-pressure side flow passage. A refrigerant that has flowed out of the first flow rate control devices 4-b and 4-c in the main circuit passes through the high-pressure side flow passage. A refrigerant obtained by merging a refrigerant which has passed through the third flow switching unit 130 at the second bypass pipe 23 and part of a refrigerant which has flowed out of the first flow rate control devices 4-b and 4-c in the main circuit and whose pressure has been reduced at the third flow rate control device 15 together at a merging point P1, passes through the low-pressure side flow passage. Preferably, the third flow rate control device 15 and the inner heat exchanger 16 are installed, in terms of improving the heating capacity. However, this configuration is not necessarily essential, and the third flow rate control device 15 and the inner heat exchanger 16 may be omitted.
Next, various operations performed by the air-conditioning apparatus 100 will be explained. The operation of the air-conditioning apparatus 100 has two types of operation modes: a cooling operation and a heating operation. Further, the heating operation includes a normal heating operation in which both the parallel heat exchangers 5-1 and 5-2, which form the outdoor heat exchanger 5, operate as normal evaporators, and a heating and defrosting operation (continuous heating operation).
In a heating and defrosting operation, defrosting of the parallel heat exchangers 5-1 and 5-2 is performed alternately while continuing a heating operation. That is, while one parallel heat exchanger is caused to operate as an evaporator and perform a heating operation, defrosting of the other parallel heat exchanger is performed. After defrosting of the other parallel heat exchanger is completed, the other parallel heat exchanger is caused to operate as an evaporator and perform a heating operation, and defrosting of the one parallel heat exchanger is performed.
Table 1 provided below illustrates ON/OFF and opening degree adjustment control of individual valves in individual operations of the air-conditioning apparatus 100 in
[Cooling Operation]
When the operation of the compressor 1 starts, a low-temperature low-pressure gas refrigerant is compressed by the compressor 1 and is discharged as a high-temperature high-pressure gas refrigerant. This refrigerant compression process at the compressor 1 is performed in such a manner that the refrigerant is heated more than when the refrigerant is adiabatically compressed based on an isentropic line by the adiabatic efficiency of the compressor 1, and is expressed by a line extending from the point (a) to the point (b) in
The high-temperature high-pressure gas refrigerant that has been discharged from the compressor 1 is split into two refrigerant streams. One refrigerant stream passes through the four-way valve 2-1 and the check valve 11-3 and flows into the parallel heat exchanger 5-1 via the second connection pipe 21-1. The other refrigerant stream passes through the solenoid valve 10-2 and flows into the parallel heat exchanger 5-2 via the second connection pipe 21-2. The refrigerant that has flowed into the parallel heat exchangers 5-1 and 5-2 is cooled down while heating up the outdoor air and is turned into a medium-temperature high-pressure liquid refrigerant. In view of pressure loss at the outdoor heat exchanger 5, the change in the refrigerant at the parallel heat exchangers 5-1 and 5-2 is expressed by a slightly-slanted substantially horizontal straight line extending from the point (b) to the point (c) in
The medium-temperature high-pressure liquid refrigerant streams that have flowed out of the parallel heat exchangers 5-1 and 5-2 flow into the first connection pipes 20-1 and 20-2, pass through the fully-opened second flow rate control devices 7-1 and 7-2, and then merge together. The merged refrigerant flows into the high-pressure side flow passage of the inner heat exchanger 16. Part of the refrigerant that has flowed out of the high-pressure side flow passage of the inner heat exchanger 16 is decompressed at the third flow rate control device 15, and then flows into the low-pressure side flow passage of the inner heat exchanger 16.
The inner heat exchanger 16 exchanges heat between the medium-temperature high-pressure liquid refrigerant that has flowed into the high-pressure side flow passage and the refrigerant that has been decompressed at the third flow rate control device 15 and flowed into the low-pressure side flow passage. At the inner heat exchanger 16, the refrigerant in the high-pressure side flow passage is cooled down by heat exchange with the refrigerant in the low-pressure side flow passage. This cooling process is expressed by a line extending from the point (c) to the point (d) in
The high-pressure liquid refrigerant that has been cooled down at the inner heat exchanger 16 passes through the second extension pipes 9-1 and 9-2, flows into the first flow rate control devices 4-b and 4-c, where the refrigerant is expanded, decompressed, and turned into a low-temperature low-pressure, two-phase gas-liquid state. The change in the refrigerant at the first flow rate control devices 4-b and 4-c occurs with a constant enthalpy. The change in the refrigerant at this time is expressed by a vertical line extending from the point (d) to the point (e) in
The refrigerant in the low-temperature low-pressure, two-phase gas-liquid state that has flowed out of the first flow rate control devices 4-b and 4-c flows into the indoor heat exchangers 3-b and 3-c. The refrigerant that has flowed into the indoor heat exchangers 3-b and 3-c is heated up while cooling down the indoor air, and is turned into a low-temperature low-pressure gas refrigerant. The first flow rate control devices 4-b and 4-c are controlled so that the superheat (degree of superheat) of the low-temperature low-pressure gas refrigerant is between about 2 K and about 5 K. In view of pressure loss, the change in the refrigerant at the indoor heat exchangers 3-b and 3-c is expressed by a slightly-slanted substantially horizontal straight line extending from the point (e) to the point (a) in
The low-temperature low-pressure gas refrigerant that has flowed out of the indoor heat exchangers 3-b and 3-c passes through the first extension pipes 8-2 and 8-1, the four-way valve 2, and the accumulator 6, and flows into the compressor 1, where the gas refrigerant is compressed.
[Normal Heating Operation]
When the operation of the compressor 1 starts, a low-temperature low-pressure gas refrigerant is compressed by the compressor 1 and is discharged as a high-temperature high-pressure gas refrigerant. This refrigerant compression process at the compressor 1 is expressed by a line extending from the point (a) to the point (b) in
The high-temperature high-pressure gas refrigerant that has been discharged from the compressor 1 passes through the four-way valve 2-1 and then flows out of the outdoor unit A. The high-temperature high-pressure gas refrigerant that has flowed out of the outdoor unit A flows into the indoor heat exchangers 3-b and 3-c of the indoor units B and C via the first extension pipes 8-1 and 8-2. The refrigerant that has flowed into the indoor heat exchangers 3-b and 3-c is cooled down while heating up the indoor air, and is turned into a medium-temperature high-pressure liquid refrigerant. The change in the refrigerant at the indoor heat exchangers 3-b and 3-c is expressed by a slightly-slanted substantially horizontal straight line extending from the point (b) to the point (c) in
The medium-temperature high-pressure liquid refrigerant that has flowed out of the indoor heat exchangers 3-b and 3-c flows into the first flow rate control devices 4-b and 4-c, where the refrigerant is expanded, decompressed, and turned into a medium-pressure, two-phase gas-liquid state. The change in the refrigerant at this time is expressed by a vertical line extending from the point (c) to the point (d) in
The refrigerant in the medium-pressure, two-phase gas-liquid state that has flowed out of the first flow rate control devices 4-b and 4-c returns to the outdoor unit A via the extension pipes 9-2 and 9-1. The refrigerant that has returned to the outdoor unit A flows into the high-pressure side flow passage of the inner heat exchanger 16. Part of the refrigerant that has returned to the outdoor unit A flows away, for the purpose of injection, from the main circuit, is decompressed at the third flow rate control device 15 (the point (d)→the point (g) in
The inner heat exchanger 16 exchanges heat between the refrigerant that has flowed into the high-pressure side flow passage and the refrigerant that has been decompressed at the third flow rate control device 15 and flowed into the low-pressure side flow passage. At the inner heat exchanger 16, the refrigerant in the high-pressure side flow passage is turned into liquid by heat exchange with the refrigerant in the low-pressure side flow passage. The change in the refrigerant at this time is expressed by a line extending from the point (d) to the point (e) in
The refrigerant in the main circuit that has passed through the high-pressure side flow passage of the inner heat exchanger 16 is split into two refrigerant streams and the refrigerant streams flow into the first connection pipes 20-1 and 20-2. The refrigerant streams that have flowed into the first connection pipes 20-1 and 20-2 are expanded, decompressed, and turned into a low-pressure, two-phase gas-liquid state by the second flow rate control devices 7-1 and 7-2. The change in the refrigerant at this time is expressed by a line extending from the point (e) to the point (f) in
The refrigerant streams that have flowed out of the second flow rate control devices 7-1 and 7-2 flow into the parallel heat exchangers 5-1 and 5-2, are heated up while cooling down the outside air, and are turned into low-temperature low-pressure gas refrigerant streams. The change in the refrigerant at the parallel heat exchangers 5-1 and 5-2 is expressed by a slightly-slanted substantially horizontal straight line extending from the point (f) to the point (a) in
[Heating and Defrosting Operation (Continuous Heating Operation)]
A heating and defrosting operation is performed in the case where frost is deposited on the outdoor heat exchanger 5 during a normal heating operation. The determination of whether or not frost has been deposited is performed, for example, by a method of determining whether a saturation temperature converted from compressor suction pressure has been significantly lowered than a specific outside air temperature.
In a heating and defrosting operation, between the case where the parallel heat exchanger 5-2 performs defrosting and the parallel heat exchanger 5-1 functions as an evaporator and continues to perform heating, and the contrary case where the parallel heat exchanger 5-2 functions as an evaporator and continues to perform heating and the parallel heat exchanger 5-1 performs defrosting, the difference is only in that the flow of a refrigerant in the parallel heat exchanger 5-1 and the flow of a refrigerant in the parallel heat exchanger 5-2 are opposite to each other by the second flow switching unit 120 and the third flow switching unit 130. Hereafter, an operation in the case where the parallel heat exchanger 5-2 performs defrosting and the parallel heat exchanger 5-1 functions as an evaporator and continues to perform heating, will be explained below.
In the case where it is detected that defrosting for resolving a frost formation state needs to be performed during execution of a normal heating operation, a controller (not illustrated) closes the second flow rate control device 7-2, which is proximity to the parallel heat exchanger 5-2 to be subjected to defrosting, in the second flow switching unit 120. Then, the controller (not illustrated) further disconnects the four-way valve 2-3, which has been connected to the parallel heat exchanger 5-2, in the first flow switching unit 110. Accordingly, the parallel heat exchanger 5-2 is disconnected from the main circuit.
Then, the controller (not illustrated) opens the solenoid valve 12-2 in the second flow switching unit 120 and the solenoid valve 12-4 in the third flow switching unit 130. Accordingly, a medium-pressure defrost circuit, in which the compressor 1, the expansion device 14, the solenoid valve 12-2, the parallel heat exchanger 5-2, the solenoid valve 12-4, the check valve 13-2, the inner heat exchanger 16, and the injection port of the compressor 1 are connected in that order, is opened, and a heating and defrosting operation is started.
Part of the high-temperature high-pressure gas refrigerant that has been discharged from the compressor 1 flows into the medium-pressure defrost circuit, and is decompressed into medium-pressure at the expansion device 14. The change in the refrigerant at this time is expressed by a line extending from the point (b) to the point (h) in
The refrigerant used for defrosting is at a saturation temperature within a range between about 0 degrees Centigrade and about 10 degrees Centigrade, which is equal to or higher than the frost temperature (0 degrees Centigrade). The refrigerant that has been used for defrosting passes through the solenoid valve 12-4 and the check valve 13-2, merges (point (j)) with the refrigerant (point (g)) that has flowed away from the main circuit and has been decompressed at the third flow rate control device 15. The merged refrigerant is heated up (point (k)) at the inner heat exchanger 16, and is injected via the injection port of the compressor 1. The check valve 13-1 prevents the refrigerant that has flowed out of the parallel heat exchanger 5-2, which is being subjected to defrosting, from flowing backward to the parallel heat exchanger 5-1, which functions as an evaporator.
In execution of injection, injection is made not to the suction side of the compressor 1 but in the middle of the compression process at the compressor 1. If injection is made to the suction side of the compressor 1, the pressure of the refrigerant to be used for defrosting needs to be reduced to the suction pressure by the expansion device 14. However, by making injection in the middle of the compression process at the compressor 1 as in this example, there is no need to reduce the pressure of the refrigerant to be used for defrosting to the suction pressure. By performing such medium-pressure defrosting, the compressor 1 only needs to increase the pressure of the refrigerant from low pressure to high pressure, which circulating in the main circuit for the purpose of heating, and the pressure of the medium-pressure, two-phase gas-liquid refrigerant that has been subjected to injection only needs to be increased from medium pressure to high pressure. Thus, the amount of load on the compressor 1 is reduced, and the efficiency (heating capacity/amount of load on the compressor) of a heat pump is improved, thereby contributing to the energy conservation effect.
The flow of a refrigerant in individual operations is clearly explained above. Now, features of the first flow switching unit 110 and the third flow switching unit 130 for switching connection on the compressor sides of the parallel heat exchangers 5-1 and 5-2 will be explained.
(First Flow Switching Unit 110)
As described above, although four-way valves and three-way valves are generally available in the market, their Cv values are in a wider range than those of solenoid valves and their costs are less expensive than solenoid valves. Therefore, if four-way valves or three-way valves are able to be used instead of known bidirectional solenoid valves for implementation of medium-pressure defrosting, the range of selection of a Cv value is widened, which enables cost reduction. In addition, with a circuit configuration in which a low-pressure low-density refrigerant which is susceptible to pressure loss passes through not a solenoid valve having a small Cv value but a four-way valve or a three-way valve, a reduction in pressure loss may be expected.
First, in order to be able to use a four-way valve or three-way vale, in the first flow switching unit 110, the four-way valves 2-2 and 2-3 are connected to the high-pressure pipe 11a, which branches off from the discharge pipe 1a, and the low-pressure pipe 11b, which branches off from the suction pipe 1b, respectively. Accordingly, high pressure and low pressure of the four-way valves 2-2 and 2-3 can be fixed.
Then, with the check valves 11-1 and 11-2, a flow passage in which only a refrigerant that has flowed out of a parallel heat exchanger functioning as an evaporator and returned to the suction side of the compressor 1 passes through the four-way valves 2-2 and 2-3 during a normal heating operation and a heating and defrosting operation, is formed. A refrigerant that has flowed out of a parallel heat exchanger functioning as an evaporator and returned to the suction side of the compressor 1, especially, has a low pressure and low density, and is susceptible to pressure loss. Therefore, with the configuration in which such a refrigerant passes through the four-way valves 2-2 and 2-3, a four-way valve having a Cv value greater than a solenoid valve can be selected, and a reduction in the pressure loss can thus be achieved. Similarly, an increase in the bore regarding a Cv value of the check valves 11-1 and 11-2 can also be achieved.
Further, the solenoid valves (unidirectional solenoid valves) 10-1 and 10-2 are provided at pipes (pipes between the high-pressure pipe 11a and the second connection pipes 21-1 and 21-2) through which a gas refrigerant passes during a cooling operation. Since a gas refrigerant has a large pressure loss at the time when passing through a pipe and a valve, it is preferable that a valve having a large Cv value is provided. However, there is a tendency that the larger the Cv value, the higher the cost. Therefore, a refrigerant passing through the solenoid valves 10-1 and 10-2 is as represented by the point (b) in
(Third Flow Switching Unit 130)
Since a liquid refrigerant is less susceptible to pressure loss at the time of passing through a valve, solenoid valves 12-3 and 12-4 having a small Cv value can be selected and used for the second bypass pipe 23 through which a small amount of liquid refrigerant after being used for defrosting passes. By replacing the solenoid valves 12-3 and 12-4 with, for example, flow rate control devices having a small Cv value and adjusting the defrosting capacity, more detailed defrost control can be performed.
As described above, in Embodiment 1, four-way valves and solenoid valves which match the characteristics of a flowing refrigerant are adopted. Thus, a refrigerant circuit configuration which achieves a reduction in cost can be attained.
Next, features of the second flow switching unit 120 will be explained.
(Second Flow Switching Unit 120)
Both during cooling and heating, a high-pressure high-density liquid refrigerant that has flowed out of a condenser flows to the first connection pipes 20-1 and 20-2. Thus, flow rate control devices 7-1 and 7-2, which correspond to the bidirectional flow of a refrigerant and are capable of controlling the flow rate, can be used, although the flow rate control devices 7-1 and 7-2 have a small Cv value. Since a refrigerant may be expanded at the solenoid valves 12-1 and 12-2, instead of by the expansion device 14, even at the time of defrosting, the solenoid valves 12-1 and 12-2, which are small in size, can be used. Thus, a refrigerant circuit configuration which matches the characteristics of a flowing refrigerant can be achieved.
Finally, a control flow for implementing the above-described operations will be explained.
Regarding division of the outdoor heat exchanger 5, in the case where the outdoor heat exchanger 5 is divided into vertically aligned portions to form the parallel heat exchangers 5-1 and 5-2 as described above, water generated by defrosting on the parallel heat exchanger arranged on an upper side, falls on the lower parallel heat exchanger operating as an evaporator. Therefore, in the case where the outdoor heat exchanger 5 is divided into vertically aligned portions, although pipe connection is more simplified than the case where the outdoor heat exchanger 5 is divided right and left, there is a possibility that ice is formed on the lower parallel heat exchanger. Thus, control for performing defrosting in the order of the upper side and then the lower side so as not to form ice in the case where the parallel heat exchanger 5-2 is arranged above the parallel heat exchanger 5-1, will be explained.
[Control Flow]
When an operation is started (S1), a determination is made as to whether a cooling operation or a heating operation is being performed based on operation modes of the indoor units B and C (S2), and control of a normal cooling operation (S3) or a normal heating operation (S4) is performed. During a heating operation, a determination as to whether or not a defrosting start condition represented by expression (1) is met (that is, whether frost is deposited or not), is performed (S5).
(Saturation temperature of suction pressure)<(Outside air temperature)−x1 (1),
where x1 may be set between about 10 K and about 20 K.
When expression (1) is met, a heating and defrosting operation is started (S6). At this time, defrosting is started first from the upper parallel heat exchanger 5-2 of the outdoor heat exchanger 5. ON/OFF states of individual valves in a normal heating operation prior to a heating and defrosting operation are represented in fields for “heating and defrosting operation” in Table 1. From the states, the states of the individual valves are changed as represented in fields for “5-1: evaporator 5-2: defrosting” in “heating and defrosting operation” in Table 1, and a heating and defrosting operation is started. More specifically, the parallel heat exchanger 5-2 is disconnected from the main circuit as described above by operations (a) and (b) described below, and defrosting is started by operations of (c) and (d) described below (S6).
(a) Second flow rate control device 7-2: close
(b) Four-way valve 2-3: OFF
(c) Solenoid valve 12-4: open
(d) Solenoid valve 12-2: open
Until frost on the parallel heat exchanger 5-2 that is subjected to defrosting is melted and a defrosting end condition is met, a heating and defrosting operation in which defrosting of the parallel heat exchanger 5-2 is performed and the parallel heat exchanger 5-1 is caused to operate as an evaporator, is performed (S7, S8). When the heating and defrosting operation continues to be performed and frost deposited on the parallel heat exchanger 5-2 starts to be melted, the temperature of a refrigerant in the second bypass pipe 23 increases. Therefore, as the defrosting end condition, for example, a temperature sensor is mounted at the second bypass pipe 23, and when the temperature of the sensor exceeds a threshold as represented by expression (2), it may be determined that defrosting should be ended.
(Temperature of refrigerant at injection pipe)>x2 (2),
where x2 may be set between 5 degrees Centigrade and 10 degrees Centigrade.
When expression (2) is met, the heating and defrosting operation for performing defrosting of the parallel heat exchanger 5-2 is ended (S9). More specifically, defrosting of the parallel heat exchanger 5-2 is ended by operations (a) and (b) described below, and the parallel heat exchanger 5-2 is reconnected to the main circuit by operations (c) and (d) described below.
(a) Solenoid valve 12-4: close
(b) Solenoid valve 12-2: close
(c) Four-way valve 2-3: ON
(d) Second flow rate control device 7-2: normal medium pressure control
Then, the states of the individual valves are changed to the states represented in fields for “5-1: defrosting 5-2: evaporator” in “heating and defrosting operation” in Table 1, and a heating and defrosting operation for performing defrosting of the parallel heat exchanger 5-1 is started. Since (S10) to (S13) differ from (S6) to (S9) only in valve numbers, explanation for (S10) to (S13) will be omitted.
As described above, by performing defrosting in the order of the upper parallel heat exchanger 5-2 and then the lower parallel heat exchanger 5-1 of the outdoor heat exchanger 5, formation of ice can be prevented. When defrosting of both the upper parallel heat exchanger 5-2 and the lower parallel heat exchanger 5-1 is completed and the heating and defrosting operation of (S6) to (S13) is ended, the process returns to the normal heating operation of (S4).
As explained above, according to Embodiment 1, a heating and defrosting operation is able to continuously heat a room while performing defrosting, and has additional advantages as described below. That is, the four-way valves 2-2 and 2-3 are connected to the high-pressure pipe 11a, which branches off from the discharge pipe 1a, and the low-pressure pipe 11b, which branches off from the suction pipe 1b, respectively. With this configuration, high pressure and low pressure can be fixed. In addition, in the first flow switching unit 110, the four-way valves 2-2 and 2-3 or three-way valves and the unidirectional solenoid valves 10-1 and 10-2 having simple configurations can be used. Thus, medium-pressure defrosting capable of high-efficiency defrosting can be achieved at low cost.
Further, among four-way valves, unidirectional solenoid valves, and bidirectional solenoid valves which are generally available in the market, the maximum Cv values decrease in the order of four-way valves, unidirectional solenoid valves, and bidirectional solenoid valves, and the price tends to increase in that order. In Embodiment 1, four-way valves and unidirectional valves are appropriately selected, in accordance with the characteristics of a flowing refrigerant, to form the first flow switching unit 110, without using bidirectional solenoid valves.
Furthermore, the solenoid valves 12-3 and 12-4, which have a small Cv value, can be selected and used for the third flow switching unit 130. Thus, cost can be reduced compared to the case where a solenoid valve having a large Cv value is used.
Further, four-way valves and unidirectional solenoid valves are appropriately selected, in accordance with the characteristics of a flowing refrigerant, to form the second flow switching unit 120, without using bidirectional solenoid valves.
In Embodiment 2, all the valves in the first flow switching unit 110 and the second flow switching unit 120 in Embodiment 1 are four-way valves.
In the air-conditioning apparatus 200, as the second connection switching devices 112-1 and 112-2 in Embodiment 1, the solenoid valves 10-1 and 10-2 are replaced with switching devices 112-1a and 112-2a described below. That is, in the switching devices 112-1a and 112-2a, check valves 11-3 and 11-4 are connected in series to third ports of four-way valves 2-1 and 2-4 whose first ports (high-pressure ports) X are connected to the high-pressure pipe 11a and second ports (low-pressure ports) Y are connected to the low-pressure pipe 11b so that a refrigerant flows only from the four-way valves 2-1 and 2-4 to the second connection pipes.
The air-conditioning apparatus 200 further includes a second flow switching unit 120a, instead of the second flow switching unit 120 in Embodiment 1. In the second flow switching unit 120a, four-way valves 18-1 and 18-2 are used, instead of the solenoid valves 12-1 and 12-2 of the second flow switching unit 120. In the four-way valves 18-1 and 18-2, first ports (high-pressure ports) X are connected to the first bypass pipe 22, second ports (low-pressure ports) Y are connected to the main pipe extending from the first flow rate control devices 4-a and 4-b toward the parallel heat exchangers 5-1 and 5-2 in the main circuit, and the connection destinations of the first connection pipes 20-1 and 20-2 are changed to the first bypass pipe 22 or the main pipe. The four-way valves 2-4, 18-1, and 18-2 may be three-way valves.
Further, the air-conditioning apparatus 200 includes a third flow switching unit 130a, instead of the third flow switching unit 130 in Embodiment 1. The third flow switching unit 130a includes a four-way valve 18-3 and the check valves 13-1 and 13-2. In the four-way valve 18-3, a first port (high pressure) is connected to the high-pressure pipe 11a, and a second port (low-pressure port) is connected to a part of the second bypass pipe 23 that is not divided into branch pipes. The check valves 13-1 and 13-2 are connected in series to a third port of the four-way valve 18-3 so that a refrigerant flows only from the second connection pipes 21-1 and 21-2 side to the second bypass pipe 23. The four-way valve 18-3 may be a three-way valve.
Table 2 provided below illustrates ON/OFF and opening degree adjustment control of individual valves in individual operations of the air-conditioning apparatus 200 in
The Cv values of the four-way valves 2-2, 2-3, and 2-4 are available in a wide range from a size for room air-conditioners to a size of air-conditioning equipment for buildings. Therefore, a valve may be selected according to the state of a refrigerant. In addition, since a circuit switching of the second flow switching unit 120 for the outdoor heat exchanger 5 is performed using the four-way valves 18-1 and 18-2, the expansion device 14 may be omitted, and expansion of a refrigerant at the time of defrosting can be adjusted by the second flow rate control device 7-1 or 7-2.
As explained above, according to Embodiment 2, effects similar to those in Embodiment 1 can be achieved.
In Embodiment 1 and Embodiment 2 described above, the outdoor heat exchanger 5 is divided into vertically aligned portions to form the parallel heat exchangers 5-1 and 5-2, and defrosting of the parallel heat exchangers 5-1 and 5-2 is performed in the order of the upper parallel heat exchanger and then the lower parallel heat exchanger during a heating and defrosting operation. Therefore, formation of ice can be prevented.
As a specific structure of the outdoor heat exchanger 5, a heat exchanger having the structure illustrated in
In
Furthermore, in the parallel heat exchangers 5-1 and 5-2, by setting the spaces between the fins of the heat exchange part 53a on the upwind side to be wider than the spaces between the fins of the heat exchange part 53b on the downwind side, the amount of heat transferred at the heat exchange part 53a on the upwind side can be efficiently transmitted to the heat exchange part 53b on the downwind side, thereby high-efficiency defrosting being achieved. The structure of the outdoor heat exchanger 5 is not limited to the structure including plural columns as illustrated in
Normally, in execution of defrosting, the outdoor fan 17 is stopped, so that the amount of heat transferred to the air is reduced. However, with this structure, even with a single outdoor fan 17 which conveys air to the parallel heat exchangers 5-1 and 5-2, defrosting can be performed without stopping the outdoor fan 17. Therefore, the heat exchange capacity of a parallel heat exchanger operating as an evaporator can be maintained.
In the case where outdoor fans are installed on the individual parallel heat exchangers 5-1 and 5-2, by stopping an outdoor fan on the side for which defrosting is performed, the amount of heat to be transferred to the air can be reduced, thereby high-efficiency defrosting can be achieved.
Furthermore, in Embodiment 1 and Embodiment 2, part of a refrigerant that has flowed out of the first flow rate control devices 4-b and 4-c takes a detour to the third flow rate control device 15, passes through the inner heat exchanger 16, and then is injected to the compressor 1. Therefore, effects described below can be achieved. That is, by cooling down a refrigerant in the main circuit through heat exchange at the inner heat exchanger 16 with a refrigerant whose pressure has been reduced at the third flow rate control device 15, the enthalpy of the refrigerant in the main circuit is reduced, and the refrigerant efficiency can be increased by the reduction of the enthalpy. Thus, an effect of improving the heating capacity can be achieved.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/004956 | 8/3/2012 | WO | 00 | 12/17/2014 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2014/020651 | 2/6/2014 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20040093893 | Tanimoto et al. | May 2004 | A1 |
| Number | Date | Country |
|---|---|---|
| 2003-202162 | Jul 2003 | JP |
| 2007-271094 | Oct 2007 | JP |
| 2007-285545 | Nov 2007 | JP |
| 2009-085484 | Apr 2009 | JP |
| 2010-014344 | Jan 2010 | JP |
| 2010-139097 | Jun 2010 | JP |
| 2012-057678 | Mar 2012 | JP |
| 2012014345 | Feb 2012 | WO |
| Entry |
|---|
| Extended Search Report dated Apr. 1, 2016 in European Patent Application No. 12882176.6. |
| International Search Report dated Oct. 16, 2012, 2013 in PCT/JP12/004956 Filed Aug. 3, 2012. |
| Number | Date | Country | |
|---|---|---|---|
| 20150292756 A1 | Oct 2015 | US |
