JP4326004B2 - Air conditioner - Google Patents

Description

  The present invention relates to an improvement in the efficiency of an air conditioner, and is particularly suitable for reducing the power of a compressor during cooling operation and heating operation.

  The suction side of the sub-compressor driven by the expansion power of the expander in order to keep the discharge side pressure of the compressor driven by the motor (motor) low, reduce the input of the motor, and improve the operating efficiency of the refrigeration cycle And the discharge side of the main compressor driven by the motor are connected in series in the refrigerant circuit to perform two-stage compression of the refrigerant, and the refrigerant compressed by the main compressor and the sub compressor is cooled by the gas cooler. For example, Patent Document 1 discloses that expansion power is recovered when the cooled high-pressure refrigerant gas is decompressed by an expander, and the recovered power is transmitted to the sub-compressor.

  In addition, in order to obtain a high power recovery effect within a wide operating range, the difference in density ratio due to refrigerant flow (operation mode) is reduced, and the efficiency of power recovery in an expander designed as a fixed density ratio is improved. In the case of the refrigerant flow using the indoor heat exchanger as an evaporator, the refrigerant sucked into the compressor by the sub compressor is supplied (charged) so that the discharge side of the sub compressor becomes the suction side of the compressor. In the case of the refrigerant flow using the indoor heat exchanger as a radiator, the refrigerant discharged from the compressor is further pressurized (expressor) so that the discharge side of the compressor becomes the suction side of the sub compressor For example, it is described in Patent Document 2.

JP 2003-279179 A (FIG. 2)

JP 2004-138332 A (FIG. 1)

  In Patent Document 1, the influence of an accumulator provided to store surplus refrigerant is not taken into account, and the density of refrigerant flowing through the low-pressure part of the refrigeration cycle is small, so that the refrigerant flow rate increases and pressure loss increases by the accumulator. However, the refrigeration capacity is reduced. Further, the excess refrigerant reduces the specific enthalpy difference in the evaporator, and even if power is recovered by the expander, the refrigeration capacity is lowered and the efficiency of the refrigeration cycle is lowered. Moreover, in patent document 2, an excess refrigerant | coolant part accumulates in a condenser, the pressure of the compressor discharge side rises, and it becomes the input increase of a compressor.

  An object of the present invention is to solve the above-described conventional technical problems and provide an air conditioner that can sufficiently obtain a power recovery effect in an expander both during cooling operation and heating operation even in an air conditioner that generates excess refrigerant. There is.

In order to achieve the above object, the present invention adopts the following configuration.
In an air conditioner in which a main compressor driven by an electric motor, a four-way valve, an outdoor heat exchanger, a liquid receiver, an indoor pressure reducing device, and an indoor heat exchanger are connected in order,
An expander provided on the outlet side of the receiver;
A sub-compressor driven by expansion power recovered by the expander and having a discharge side connected to a suction side of the main compressor;
A bridge circuit which is provided between the outdoor heat exchanger and the liquid receiver, and in which a check valve is combined so that the refrigerant passes through the expander via the liquid receiver during cooling and heating operations;
A subcooling heat exchanger provided between the expander and the bridge circuit and provided with a main flow portion and a sub flow portion;
One of the main flow portions is piped to the expander outlet, the other is connected to the bridge circuit, and one of the subflow portions is bypassed from a pipe connecting the expander and the main flow portion, and is connected via a supercooling expansion valve. An air conditioner, wherein the other is connected to a subcooling bypass return pipe that joins a pipe connecting the four-way valve and the suction side of the sub compressor.

In addition, the following configuration was adopted.
In an air conditioner in which a main compressor driven by an electric motor, a four-way valve, an outdoor heat exchanger, a liquid receiver, an indoor pressure reducing device, and an indoor heat exchanger are connected in order,
An expander provided on the outlet side of the receiver;
A sub-compressor driven by expansion power recovered by the expander and having a discharge side connected to a suction side of the main compressor;
A bridge circuit which is provided between the outdoor heat exchanger and the liquid receiver, and in which a check valve is combined so that the refrigerant passes through the expander via the liquid receiver during cooling and heating operations;
A subcooling heat exchanger provided between the expander and the bridge circuit and provided with a main flow portion and a sub flow portion;
One of the main flow portions is piped to the expander outlet, the other is connected to the bridge circuit, and one of the subflow portions is bypassed from a pipe connecting the expander and the main flow portion, and is connected via a supercooling expansion valve. An air conditioner characterized in that the other is connected to a supercooling bypass return pipe connected to the suction side of the main compressor.

According to the present invention, the amount of decompression in the expander is maximized during both the cooling operation and the heating operation, while preventing a decrease in refrigeration capacity due to an increase in pressure loss on the compressor suction side and a decrease in specific enthalpy difference in the evaporator. Therefore, the expansion power that can be recovered by the expander can be utilized to the maximum extent in the sub-compressor.
Moreover, since the compression ratio of the main compressor driven by the electric motor can be reduced and the refrigerant density sucked into the main compressor can be increased, the power in the main compressor can be reduced. As a result, the refrigeration capacity can be increased, and the increased efficiency of the air conditioner can be further improved by utilizing the increased refrigeration capacity for reducing the power of the main compressor driven by the electric motor.

  In recent years, a refrigeration cycle apparatus using carbon dioxide as a refrigerant, which has an ozone depletion coefficient of zero and a global warming coefficient much smaller than that of fluorocarbons, has attracted attention. The carbon dioxide refrigerant has a critical temperature as low as 31.06 ° C., and when a temperature higher than this temperature is used, the carbon dioxide refrigerant is used on the high pressure side (compressor outlet to radiator to decompressor inlet) of the refrigeration cycle apparatus. Therefore, the operation efficiency of the refrigeration cycle apparatus is reduced as compared with a conventional chlorofluorocarbon refrigerant. For this reason, in order to improve the operating efficiency of the refrigeration cycle in the supercritical state, an expander is provided as a decompression device for the refrigeration cycle, and the expansion power recovered by the expander is used as part of the compressor driving force. Various methods have been proposed, and a method of providing a sub-compressor driven by expansion power recovered by an expander at a position where two-stage compression is performed.

An embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a refrigeration cycle system diagram of an air conditioner equipped with an expander and an auxiliary compressor driven by expansion power recovered by the expander according to an embodiment of the present invention. The outdoor unit is configured by connecting a main compressor 1 driven by an electric motor 9, a four-way valve 2, an outdoor heat exchanger 3, a liquid receiver 4, a liquid blocking valve 8, and a gas blocking valve 7. The indoor unit includes an indoor expansion valve 5 and an indoor heat exchanger 6, and is connected to a gas blocking valve 7 and a liquid blocking valve 8 attached to the outdoor unit by piping.

  In the outdoor unit, an expander 11 is provided on the downstream side of the liquid receiver 4, and a power transmission shaft 13 is attached to the expander 11, and the other end of the power transmission shaft 13 is a drive shaft of the sub compressor 12. The sub compressor 12 is driven by the expansion power of the expander 11. The sub-compressor 12 is provided between the four-way valve 2 and the main compressor 1, and the four-way valve 2 and the suction side of the sub-compressor 12 are connected by piping, and the discharge side of the sub-compressor 12 and the suction of the main compressor 1 are connected. The pipe is connected to the side. In addition, a check is made between the outdoor heat exchanger 3 and the liquid receiver 4 so that the flow direction of the refrigerant from the liquid receiver 4 to the expander 11 is the same in both the cooling operation and the heating operation. The bridge circuit 10 is configured by combining four valves as shown in the figure.

Next, the flow state of the refrigerant in the refrigeration cycle will be described. In FIG. 1, the flow direction of the refrigerant is indicated by a solid line arrow in the heating operation and a broken line arrow in the cooling operation.
In the case of the cooling operation, the high-temperature and high-pressure gas refrigerant compressed by the main compressor 1 driven by the electric motor 9 flows into the outdoor heat exchanger 3 through the four-way valve 2, and exchanges heat with the outside air in the outdoor heat exchanger 3. As a result, the heat is condensed and discharged as liquid refrigerant, and flows into the receiver 4 through the bridge circuit 10. In the liquid receiver 4, surplus refrigerant is stored in the operation of the refrigeration cycle, and the liquid refrigerant flowing out of the liquid receiver 4 is isentropically depressurized by the expander 11 to be in an intermediate pressure state between high pressure and low pressure. The pressure is reduced by the indoor expansion valve 5 through the circuit 10 and the liquid blocking valve 8 to be in a low pressure state, and flows into the indoor heat exchanger 6.

  In the indoor heat exchanger 6, the heat is evaporated by exchanging heat with the room air, flows out as a low-pressure gas refrigerant, passes through the gas blocking valve 7 and the four-way valve 2, and is sucked into the sub-compressor 12. Since the subcompressor 12 is connected to the expander 11 by the power transmission shaft 13, the gas refrigerant driven by the expansion power in the expander 11 and sucked into the subcompressor 12 is compressed by the amount of expansion power. The compressed gas refrigerant is sucked into the main compressor 1.

  In the heating operation, the high-temperature and high-pressure gas refrigerant compressed by the main compressor 1 driven by the electric motor 9 flows into the indoor heat exchanger 6 through the four-way valve 2 and the gas blocking valve 7, and the indoor heat exchanger 6 Then, heat exchange with room air causes heat radiation to condense and flow out into liquid refrigerant, and flows into the liquid receiver 4 through the indoor expansion valve 5, liquid blocking valve 8 and bridge circuit 10. In the liquid receiver 4, surplus refrigerant is stored for capacity generation, and the liquid refrigerant flowing out of the liquid receiver 4 is isentropically decompressed by the expander 11 to be in a low pressure state and passes through the bridge circuit 10 to perform outdoor heat exchange. Flows into the vessel 3. In the outdoor heat exchanger 3, the heat is evaporated by exchanging heat with the outside air and flows out as a low-pressure gas refrigerant, and is sucked into the sub compressor 12 through the four-way valve 2. Since the sub-compressor 12 is connected to the expander 11 by the power transmission shaft 13, the gas refrigerant driven by the expansion power in the expander 11 and sucked into the sub-compressor 12 is compressed by the amount of expansion power. The compressed gas refrigerant is sucked into the main compressor 1.

  By configuring the bridge circuit 10 so that the expander 11 is always on the downstream side of the liquid receiver 4 during both the cooling operation and the heating operation, the surplus refrigerant is stored in the liquid receiver 4 and the optimum refrigerant amount is obtained. While supplying the refrigeration cycle, the pressure difference between the front and rear of the expander 11 can be secured, and the expansion power recoverable by the expander 11 can be maximized. Thereby, the compression power in the main compressor 1 driven by the electric motor 9 is used as the compression power in the sub-compressor 12 driven by the expansion power in the expander 11, that is, the expansion, during both the cooling operation and the heating operation. The power can be reduced and the efficiency of the refrigeration cycle is improved.

  In addition, since the sub compressor 12 is disposed on the low pressure side of the main compressor 1, the state of the refrigerant sucked into the main compressor 1 is higher than that without the sub compressor 12. The density of the refrigerant sucked into the main compressor 1 increases. And the discharge amount in the main compressor 1 can be decreased, and the compression power in the main compressor 1 can further be reduced. Furthermore, since the ratio between the high-pressure side pressure and the low-pressure side pressure of the main compressor 1 is reduced by the amount of pressure increase in the sub-compressor 12 compared to the case where there is no sub-compressor 12, the compression efficiency of the main compressor 1 is reduced. And the compression power in the main compressor 1 can be reduced, so that the efficiency of the refrigeration cycle can be improved.

  Further, the bridge circuit 10 including four check valves can be replaced with a second four-way valve 14 as shown in FIG.

Next, another embodiment of the present invention will be described with reference to FIGS.
FIG. 3 is a refrigeration cycle diagram of an air conditioner showing another embodiment. The supercooling heat exchanger 15 is provided between the expander 11 and the bridge circuit 10 and supercools the refrigerant flowing out of the expander 11. The subcooling heat exchanger 15 is provided with a main flow portion and a sub flow portion, and each performs heat exchange with a refrigerant flowing through the main flow portion and the sub flow portion. One of the main flow portions is pipe-connected to the outlet of the expander 11 and the other is connected to the bridge circuit 10. A bypass pipe is provided from a pipe connecting the expander 11 and the supercooling heat exchanger 15, and the pipe is connected to one of the subflow portions via the supercooling expansion valve 16. The other of the subflow portions is connected by a supercooling bypass return pipe 17 so as to join a pipe connecting the four-way valve 2 and the suction side of the subcompressor 12.

  Next, the flow state of the refrigerant in the refrigeration cycle will be described. As in FIG. 1, the flow direction of the refrigerant is indicated by a solid arrow in the heating operation and by a broken arrow in the cooling operation. The refrigerant flow and state up to the expander 11 during both the cooling operation and the heating operation are the same as those in the embodiment shown in FIG.

  The refrigerant that is isentropically depressurized by the expander 11 is divided into two before the supercooling heat exchanger 15, one is further depressurized by the supercooling expansion valve 16, one at the main flow portion of the supercooling heat exchanger 15. Then, the refrigerant flows into the sidestream portion and exchanges heat between the refrigerant flowing through the mainstream portion and the refrigerant flowing through the sidestream portion, so that the temperature of the refrigerant flowing through the mainstream portion is lowered and supercooled liquid is generated. In addition, the refrigerant flowing in the substream portion absorbs heat from the refrigerant flowing in the mainstream portion and is superheated to become a gas refrigerant, and merges with the refrigerant flowing on the suction side of the subcompressor 12.

  As described above, since the specific enthalpy difference on the evaporation side can be increased by supercooling the refrigerant flowing out of the expander 11 by the supercooling heat exchanger 15, the expansion power is increased by the expander 11 while improving the evaporation performance. And the efficiency of the refrigeration cycle can be improved. In addition, the amount of refrigerant flowing in the evaporator (the indoor heat exchanger during cooling operation and the outdoor heat exchanger during heating operation) can be reduced by the amount of refrigerant flowing in the sub-flow part of the supercooling heat exchanger. The pressure loss of the refrigeration cycle can be improved.

  Further, instead of joining the other side of the auxiliary flow part of FIG. 3 to the pipe connecting the four-way valve 2 and the suction side of the auxiliary compressor 12, as shown in FIG. By returning to the suction side of the main compressor 1, the amount of refrigerant compressed by the sub compressor 12 can be reduced as compared with that shown in FIG. Therefore, more of the expansion power recovered by the expander 11 can be used for the compression power of the sub-compressor 12, and the efficiency of the refrigeration cycle can be further improved.

In addition, as shown in FIG. 5, the power transmission shaft 13 provided in the expander 11 and the shaft of the electric motor (motor) 9 may be coaxial instead of the sub compressor 12, and in this case, the sub compressor 12 Therefore, the manufacturing cost of the air conditioner can be greatly reduced.
Further, as shown in FIG. 6, the suction side of the main compressor 1 driven by the four-way valve 2 and the electric motor (motor) 9 is connected, and the discharge power of the main compressor 1 and the expansion power recovered by the expander 11 are connected. In this case, since the density of the refrigerant sucked into the sub compressor 12 is reduced, the compression chamber of the sub compressor 12 can be reduced. The sub compressor 12 can be reduced in size and weight. And it becomes advantageous to reduce the manufacturing cost of an air conditioning apparatus.

  In the above air conditioner, the effect of improving the efficiency of the refrigeration cycle is increased when a refrigerant that forms a supercritical cycle such as carbon dioxide is used as the refrigerant. However, when a chlorofluorocarbon refrigerant such as HFC is used, Efficiency can be improved.

The refrigerating cycle system diagram of the air conditioning apparatus which shows one Embodiment of this invention. The refrigeration cycle system | strain diagram of the air conditioning apparatus which shows other embodiment. Furthermore, the refrigeration cycle system | strain diagram of the air conditioning apparatus which shows other embodiment. Furthermore, the refrigeration cycle system | strain diagram of the air conditioning apparatus which shows other embodiment. Furthermore, the refrigeration cycle system | strain diagram of the air conditioning apparatus which shows other embodiment. Furthermore, the refrigeration cycle system | strain diagram of the air conditioning apparatus which shows other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Main compressor, 2 ... Four-way valve, 3 ... Outdoor heat exchanger, 4 ... Liquid receiver, 5 ... Indoor expansion valve, 6 ... Indoor heat exchanger, 9 ... Electric motor (motor), 10 ... Bridge circuit, 11 DESCRIPTION OF SYMBOLS ... Expander, 12 ... Subcompressor, 13 ... Power transmission shaft, 14 ... Second four-way valve, 15 ... Supercooling heat exchanger, 16 ... Supercooling expansion valve, 17 ... Supercooling bypass return piping.

Claims (4)

In an air conditioner in which a main compressor driven by an electric motor, a four-way valve, an outdoor heat exchanger, a liquid receiver, an indoor pressure reducing device, and an indoor heat exchanger are connected in order ,
An expander provided on the outlet side of the receiver;
A sub-compressor driven by expansion power recovered by the expander and having a discharge side connected to a suction side of the main compressor;
A bridge circuit which is provided between the outdoor heat exchanger and the liquid receiver, and in which a check valve is combined so that the refrigerant passes through the expander via the liquid receiver during cooling and heating operations;
Provided between the front Symbol expander and said bridge circuit, and a main portion and a side stream portion is provided supercooling heat exchanger,
One of the main flow portions is piped to the expander outlet, the other is connected to the bridge circuit, and one of the subflow portions is bypassed from a pipe connecting the expander and the main flow portion, and is connected via a supercooling expansion valve. An air conditioner, wherein the other is connected to a subcooling bypass return pipe that joins a pipe connecting the four-way valve and the suction side of the sub compressor. In an air conditioner in which a main compressor driven by an electric motor, a four-way valve, an outdoor heat exchanger, a liquid receiver, an indoor pressure reducing device, and an indoor heat exchanger are connected in order ,
An expander provided on the outlet side of the receiver;
A sub-compressor driven by expansion power recovered by the expander and having a discharge side connected to a suction side of the main compressor;
A bridge circuit which is provided between the outdoor heat exchanger and the liquid receiver, and in which a check valve is combined so that the refrigerant passes through the expander via the liquid receiver during cooling and heating operations;
Provided between the front Symbol expander and said bridge circuit, and a main portion and a side stream portion is provided supercooling heat exchanger,
One of the main flow portions is piped to the expander outlet, the other is connected to the bridge circuit, and one of the subflow portions is bypassed from a pipe connecting the expander and the main flow portion, and is connected via a supercooling expansion valve. An air conditioner characterized in that the other is connected to a supercooling bypass return pipe connected to the suction side of the main compressor. 3. The method according to claim 1 , wherein, instead of the bridge circuit, a second four-way valve is used to allow refrigerant to pass through the expander via the liquid receiver during both cooling operation and heating operation. Air conditioner. The air conditioner according to any one of claims 1 to 3 , wherein the refrigerant used in the air conditioner is a chlorofluorocarbon refrigerant.

Images