JP6916716B2 - heat pump - Google Patents

Description

The present invention relates to a heat pump provided with a refrigerant circuit.

Conventionally, a refrigeration cycle, that is, a heat pump, in which a refrigerant circuit in which a refrigerant repeatedly circulates by compression and expansion is provided is known. In such a heat pump, for example, as described in Patent Document 1, a low-stage compressor that compresses the refrigerant and a high-stage compressor that further compresses the refrigerant discharged from the low-stage compressor are used. The refrigerant may be compressed in two stages.

Such a heat pump is provided with an evaporator that evaporates the refrigerant on the upstream side of the low-stage compressor. The evaporator is, for example, a heat exchanger in which heat exchange is performed between a refrigerant and a heat medium such as water or air.

Japanese Unexamined Patent Publication No. 2016-90102

Here, in the heat pump of Patent Document 1, the refrigerant from the evaporator is introduced into the low-stage compressor, and then is introduced into the high-stage compressor.
However, the amount of heat exchanged in the evaporator is not always constant and may fluctuate due to environmental factors and the like. Therefore, the temperature of the refrigerant introduced from the heat exchanger into the low-stage compressor is not constant, and the refrigerant introduced into the low-stage compressor is not in the optimum state for compression in the low-stage compressor. Therefore, it may not be possible to operate the heat pump as a whole efficiently.
Further, when the refrigerant from the evaporator contains a liquid phase, there is a risk of liquid compression occurring in the low-stage compressor and the high-stage compressor, and it is also difficult to perform efficient operation.

Therefore, the present invention provides a heat pump capable of efficient operation by introducing a refrigerant in an optimum state for compression into a low-stage compressor and a high-stage compressor.

The heat pump according to the first aspect of the present invention includes a low-stage compressor, a high-stage compressor connected in series to the downstream side of the low-stage compressor, and a downstream side of the high-stage compressor. A condenser connected to, an expansion mechanism connected to the downstream side of the condenser, an evaporator connected to the downstream side of the expansion mechanism, and from the evaporator to the low-stage compressor and the high-stage compressor. A switching valve that allows the refrigerant to be selectively introduced into one of the side compressors and a switching valve provided at the inlet of the low-stage compressor are provided to separate the liquid phase of the compressor and compress the gas phase on the low-stage side. A low-stage gas-liquid separator that can be introduced into the machine and an inlet of the high-stage compressor are provided to separate the liquid phase of the refrigerant so that the gas phase can be introduced into the high-stage compressor. A high-stage gas-liquid separator and a plurality of the evaporators are provided, and the switching valve is selectively provided from the evaporator to one of the low-stage compressor and the high-stage compressor. It is provided corresponding to each of the compressors so that a refrigerant can be introduced .

According to such a heat pump, the refrigerant can be selectively introduced from the evaporator to either the low-stage compressor or the high-stage compressor. Therefore, the introduction path of the refrigerant can be switched to the compressor capable of optimum compression according to the state of the refrigerant flowing out from each evaporator.
Further, regardless of whether the refrigerant from the evaporator is introduced into the low-stage compressor or the high-stage compressor, gas-liquid separation from the refrigerant is performed at the inlet of the low-stage compressor at the low-stage side air. After performing the gas-liquid separation from the refrigerant at the inlet of the high-stage compressor with the liquid separator, or after performing the gas-liquid separation from the refrigerant with the high-stage gas-liquid separator, the gas phase is compressed with the low-stage compressor or the high-stage side. It will be possible to introduce it to the machine.
Further, since a plurality of evaporators are provided in this way, the heat pump has a multi-source type refrigerant circuit including a plurality of heat exchangers having different heat exchange amounts and installation environments.
Here, in each evaporator, the amount of heat exchange fluctuates and the temperature of the refrigerant changes, so that the state of the refrigerant toward the low-stage compressor and the high-stage compressor changes to these low-stage compressors and high-stage compressors. It may not be in the optimum state for compression by the side compressor. Therefore, in this embodiment, not only the refrigerant can be introduced from each evaporator to the low-stage compressor by the switching valve, but also the refrigerant can be directly introduced into the high-stage compressor by bypassing the low-stage compressor. ..
Further, at the same time as switching the introduction path of the refrigerant from one evaporator to the compressor, it is possible to switch the introduction path of the refrigerant from the other evaporator to the compressor. Therefore, the introduction path of the refrigerant can be switched to the compressor capable of optimum compression according to the state of the refrigerant flowing out from each evaporator.

The heat pump according to the second aspect of the present invention further includes an interstage flow path between the low-stage compressor and the high-stage compressor in the first aspect, and the high-stage gas-liquid The separator may be provided in the interstage flow path.

In this way, when the high-stage gas-liquid separator is provided in the interstage flow path, the refrigerant from the evaporator is introduced into the high-stage compressor via the low-stage compressor. , Gas-liquid separation of the refrigerant can be performed, and the risk of liquid compression in the high-stage compressor can be further reduced.

The heat pump according to the third aspect of the present invention is a high-stage flow path that connects the evaporator and the high-stage compressor without passing through the low-stage compressor in the first aspect. The high-stage gas-liquid separator may be provided in the high-stage flow path.

When the refrigerant from the evaporator is introduced into the high-stage compressor via the low-stage compressor, the refrigerant does not flow through the high-stage flow path. In this case, since the high-stage gas-liquid separator is provided in the high-stage flow path, the refrigerant does not pass through the high-stage gas-liquid separator. Therefore, it is possible to avoid the pressure loss that occurs when the refrigerant discharged from the low-stage compressor passes through the high-stage gas-liquid separator. Therefore, COP (Coefficient Of Performance) in the heat pump, that is, the operation efficiency can be improved.

According to the above heat pump, the refrigerant in the optimum state for compression is introduced into the low-stage compressor and the high-stage compressor, and efficient operation becomes possible.

It is an overall block diagram of the heat pump of the 1st Embodiment of this invention. It is an overall block diagram of the heat pump of the 2nd Embodiment of this invention.

Hereinafter, the heat pump 1 according to the first embodiment of the present invention will be described.
As shown in FIG. 1, the heat pump 1 according to the present embodiment has a refrigerant circuit 2 that operates in a two-stage compression cycle. The refrigerant circuit 2 has a low-stage compressor 3, a high-stage compressor 4, a condenser 5, an expansion valve (expansion mechanism) 6, and an evaporator 10, and these components are connected by a pipe 15 in this order. Has been done. Then, a refrigerant R such as carbon dioxide circulates in the refrigerant circuit 2. Here, the refrigerant R is not particularly limited to carbon dioxide.

The low-stage compressor 3 sucks in the refrigerant R and compresses the refrigerant R. The low-stage compressor 3 is, for example, a rotary compressor or a scroll compressor.

The high-stage compressor 4 is connected in series with the low-stage compressor 3 and further compresses the refrigerant R discharged from the low-stage compressor 3 to a higher pressure. The pipe 15 between the low-stage compressor 3 and the high-stage compressor 4 is an interstage flow path CM. The high-stage compressor 4 is, for example, a rotary compressor or a scroll compressor.

The condenser 5 exchanges heat between the high-temperature and high-pressure refrigerant R discharged from the high-stage compressor 4 and the heat medium R1 such as air or water to cool and condense the refrigerant R.

The expansion valve 6 adiabatically expands the refrigerant R from the condenser 5, and depressurizes the refrigerant R. A plurality of expansion valves 6 (two in this embodiment) are provided on the upstream side (inlet side) of the evaporator 10 corresponding to the first evaporator 11 and the second evaporator 12, which will be described later.

As the evaporator 10, the first evaporator 11 and the second evaporator 12 are provided in the present embodiment. The first evaporator 11 and the second evaporator 12 are provided in parallel. However, the quantity of the evaporator 10 is not limited to the case of this embodiment.

The first evaporator 11 is an air heat exchanger that exchanges heat between the refrigerant R that has passed through the expansion valve 6 and, for example, air as the heat medium R2.

The pipe 15 between the first evaporator 11 and the upstream side (suction side) of the low-stage compressor 3 is the first flow path C1. The first flow path C1 is provided with a first valve portion 17 capable of switching the flow direction of the refrigerant R. In this embodiment, the first valve portion 17 is a four-way valve.

Further, the pipe 15 between the first evaporator 11 and the upstream side of the high-stage compressor 4 (the suction side of the high-stage compressor 4 and the discharge side of the low-stage compressor 3) is the first. It has two flow paths (high-stage flow paths) C2. Here, a second valve portion (switching valve) 18 is provided in the first flow path C1 at a position between the first valve portion 17 and the first evaporator 11. The second flow path C2 connects the second valve portion 18 and the interstage flow path CM. The second valve portion 18 is a three-way valve. The second valve portion 18 makes it possible to switch the flow direction of the refrigerant R depending on whether the refrigerant R flows toward the downstream of the first flow path C1 or toward the second flow path C2. When the refrigerant R flows through the second flow path C2, the refrigerant R does not pass through the low-stage compressor 3.

The second evaporator 12 is a water heat exchanger that exchanges heat between the refrigerant R that has passed through the expansion valve 6 and, for example, water as the heat medium R3.

The pipe 15 between the second evaporator 12 and the upstream side (suction side) of the low-stage compressor 3 is a third flow path C3. Specifically, the third flow path C3 has an upstream side portion C3a connecting the outlet on the downstream side of the second evaporator 12 and the first flow path C1 at a position upstream of the first valve portion 17. is doing. Further, the third flow path C3 has a downstream side portion C3b that connects the first valve portion 17 and the upstream side inlet of the low-stage compressor 3. Further, a third valve portion (switching valve) 19 is provided on the upstream side portion C3a. In the present embodiment, the second valve portion 18 and the third valve portion 19 are three-way valves, but the present invention is not limited to this, and any valve that can switch the flow direction of the refrigerant R may be used.

Further, the pipe 15 between the second evaporator 12 and the inlet on the upstream side of the high-stage compressor 4 is a fourth flow path (high-stage flow path) C4. The fourth flow path C4 connects the third valve portion 19 and the intermediate position of the second flow path C2 to the third valve portion 19 and the interstage flow path CM via the second flow path C2. Is connected. The third valve portion 19 makes it possible to switch the flow direction of the refrigerant R depending on whether the refrigerant R flows toward the downstream side of the upstream side portion C3a or toward the fourth flow path C4. When the refrigerant R flows through the fourth flow path C4, the refrigerant R does not pass through the low-stage compressor 3.

Here, the refrigerant circuit 2 further includes a low-stage gas-liquid separator 21 and a high-stage gas-liquid separator 22.
The low-stage gas-liquid separator 21 is a device called an accumulator, which is provided at the inlet of the low-stage compressor 3 and on the downstream side C3b of the third flow path C3. The low-stage gas-liquid separator 21 separates the liquid phase of the refrigerant R at the inlet of the low-stage gas-liquid separator 21 so that the gas phase can be introduced into the low-stage compressor 3. The liquid phase of the refrigerant R separated by the low-stage gas-liquid separator 21 may be introduced into the low-stage compressor 3 by a device (not shown).

Like the low-stage gas-liquid separator 21, the high-stage gas-liquid separator 22 is a device called an accumulator, and is between the outlet of the low-stage compressor 3 and the inlet of the high-stage compressor 4. It is provided in the interstage flow path CM. The high-stage gas-liquid separator 22 separates the liquid phase of the refrigerant R so that the gas phase can be introduced into the high-stage compressor 4. The liquid phase of the refrigerant R separated by the high-stage gas-liquid separator 22 may be introduced into the high-stage compressor 4 by a device (not shown).

According to the heat pump 1 of the present embodiment described above, the refrigerant R is selectively introduced from the first evaporator 11 and the second evaporator 12 into either the low-stage compressor 3 or the high-stage compressor 4. Can be made to.

Specifically, when switching between the case where the refrigerant R is introduced from the first evaporator 11 into the low-stage compressor 3 and the case where the refrigerant R is introduced into the high-stage compressor 4, the second valve portion Operate 18. The operation of the second valve portion 18 may be performed by a control unit (not shown) or manually.

Further, when switching between the case where the refrigerant R is introduced from the second evaporator 12 into the low-stage compressor 3 and the case where the refrigerant R is introduced into the high-stage compressor 4, the third valve portion 19 is operated. do. The operation of the third valve portion 19 may be performed by a control unit (not shown) or may be performed manually.

By appropriately changing the flow path of the refrigerant R from the first evaporator 11 and the second evaporator 12 in this way, the lower stage side compressor 3 and the higher stage compressor 3 can be changed according to the state of the refrigerant R flowing out from each evaporator 10. Of the stage side compressors 4, the refrigerant R can be introduced into a compressor capable of optimum compression.

Further, regardless of whether the refrigerant R from the evaporator 10 (11, 12) is introduced into either the low-stage compressor 3 or the high-stage compressor 4, the low-stage gas-liquid separator 21 After the gas-liquid separation of the refrigerant R is performed at the inlet of the low-stage compressor 3 or the gas-liquid separation of the refrigerant R is performed at the inlet of the high-stage compressor 4 by the high-stage side compressor 22. , The gas phase can be introduced into the low-stage compressor 3 or the high-stage compressor 4. That is, regardless of whether the refrigerant R is introduced from the first evaporator 11 or the second evaporator 12 into either the low-stage compressor 3 or the high-stage compressor 4, gas-liquid separation of the refrigerant R is always performed. It is said.
Therefore, the refrigerant R in the optimum state for compression can be introduced into the low-stage compressor 3 and the high-stage compressor 4, and the liquid compression in the low-stage compressor 3 and the high-stage compressor 4 can be avoided. Therefore, efficient operation is possible.

Further, in the present embodiment, since a plurality of evaporators 10 are provided, the heat pump 1 has a multi-source type refrigerant circuit 2 having a plurality of heat exchangers having different heat exchange amounts and installation environments. ..

Here, in each of the first evaporator 11 and the second evaporator 12, the heat exchange amount fluctuates and the temperature of the refrigerant R changes, so that the compressor 3 moves toward the low-stage compressor 3 and the high-stage compressor 4 moves toward the high-stage compressor 4. The state of the refrigerant R may not be the optimum state for compression by the low-stage compressor 3 and the high-stage compressor 4. Therefore, in the present embodiment, the second valve portion 18 and the third valve portion 19 not only introduce the refrigerant R from each evaporator 10 to the lower stage compressor 3, but also bypass the lower stage compressor 3. The refrigerant R can be directly introduced into the high-stage compressor 4. Therefore, efficient operation is possible.

Further, it is possible to switch the flow path of the refrigerant R from the second evaporator 12 at the same time as switching the flow path of the refrigerant R from the first evaporator 11. Therefore, depending on the state of the refrigerant R flowing out from each of the first evaporator 11 and the second evaporator 12, the compressor capable of optimal compression among the low-stage side compressor 3 and the high-stage side compressor 4 The introduction path of the refrigerant R can be switched. Therefore, it is possible to improve the operating efficiency.

[Second Embodiment]
Next, the heat pump 1A of the second embodiment of the present invention will be described with reference to FIG. In the second embodiment described below, the same parts as those in the first embodiment will be described with the same reference numerals, and duplicate description will be omitted. In the second embodiment, the installation location of the high-stage gas-liquid separator 22A is different from that in the first embodiment.

The high-stage gas-liquid separator 22A is provided in the second flow path C2 at the inlet of the high-stage compressor 4. That is, when the refrigerant R is introduced from the first evaporator 11 (second evaporator 12) into the high-stage compressor 4 without passing through the low-stage compressor 3, the refrigerant R does not pass through the low-stage compressor 3. The high-stage side gas-liquid separator 22A is provided before (upstream side) where the refrigerant R and the refrigerant R discharged from the low-stage compressor 3 merge.

According to the heat pump 1A of the present embodiment, when the refrigerant R from the first evaporator 11 is introduced into the high-stage compressor 4 without passing through the low-stage compressor 3, the high-stage side air The liquid separator 22A can separate the refrigerant R into gas and liquid, and the gas phase can be introduced into the high-stage compressor 4. Therefore, the risk of liquid compression in the high-stage compressor 4 can be reduced.
Further, since the high-stage gas-liquid separator 22A is provided in the second flow path C2, the refrigerant R from the first evaporator 11 and the second evaporator 12 passes through the low-stage compressor 3. When introduced into the high-stage compressor 4, the refrigerant R does not flow through the second flow path C2. Therefore, in this case, since the refrigerant R does not pass through the high-stage gas-liquid separator 22A, pressure loss occurs due to the refrigerant R discharged from the low-stage compressor 3 passing through the high-stage gas-liquid separator 22A. Can be avoided. Therefore, it is possible to improve the COP of the heat pump 1A, that is, the operating efficiency.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the configurations and combinations thereof in the respective embodiments are examples, and the configurations are added or omitted within the range not deviating from the gist of the present invention. , Replacement, and other changes are possible. Further, the present invention is not limited to the embodiments, but only to the scope of claims.
For example, in the above embodiment, an example in which the first evaporator 11 and the second evaporator 12 are provided as the evaporator 10 has been described, but the number of evaporators 10 is not limited to the case of the above embodiment and is one. Only may be provided, or three or more may be provided.

1, 1A ... Heat pump 2 ... Refrigerant circuit 3 ... Low-stage compressor 4 ... High-stage compressor 5 ... Condenser 6 ... Expansion valve 10 ... Evaporator 11 ... First evaporator 12 ... Second evaporator 15 ... Piping 17 ... First valve portion 18 ... Second valve portion (switching valve)
19 ... Third valve (switching valve)
21 ... Low-stage gas-liquid separators 22, 22A ... High-stage gas-liquid separator R1 ... Heat medium R2 ... Heat medium R3 ... Heat medium C1 ... First flow path C2 ... Second flow path (high-stage flow path)
C3 ... Third flow path C3a ... Upstream side C3b ... Downstream side C4 ... Fourth flow path (high-stage flow path)
CM ... Interstage flow path R ... Refrigerant

Claims (3)

Low-stage compressor and
A high-stage compressor connected in series to the downstream side of the low-stage compressor,
A condenser connected to the downstream side of the high-stage compressor and
An expansion mechanism connected to the downstream side of the condenser and
An evaporator connected to the downstream side of the expansion mechanism and
A switching valve that allows the refrigerant to be selectively introduced from the evaporator to one of the low-stage compressor and the high-stage compressor.
Wherein provided on the inlet of the low-stage compressor, a low-stage gas-liquid separator which enables introduction of the gas phase to separate the liquid phase of the said coolant in the low-stage compressor,
Provided to the inlet of the high stage side compressor, a high-stage gas-liquid separator which enables introduction of the gas phase to separate the liquid phase of the said coolant in the high-pressure stage compressor,
Equipped with a,
A plurality of the evaporators are provided,
The switching valve is provided corresponding to each of the evaporators so that the refrigerant can be selectively introduced from the evaporator to one of the low-stage compressor and the high-stage compressor. The heat pump that is being used. An interstage flow path is further provided between the low-stage compressor and the high-stage compressor.
The heat pump according to claim 1, wherein the high-stage gas-liquid separator is provided in the interstage flow path. A high-stage flow path for connecting the evaporator and the high-stage compressor without passing through the low-stage compressor is further provided.
The heat pump according to claim 1, wherein the high-stage gas-liquid separator is provided in the high-stage flow path.

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