CN111316047A

CN111316047A - Heat pump

Info

Publication number: CN111316047A
Application number: CN201880072403.3A
Authority: CN
Inventors: 小林隆之; 葛山洋平; 中山浩; 德永康治
Original assignee: Kansai Electric Power Co Inc; Chubu Electric Power Co Inc; Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Kansai Electric Power Co Inc; Chubu Electric Power Co Inc; Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2017-11-08
Filing date: 2018-11-08
Publication date: 2020-06-19
Also published as: EP3708924A1; WO2019093420A1; EP3708924A4; JP2019086238A; JP6373469B1

Abstract

The refrigerant circuit (2) has: a first channel (C1) and a first valve unit (21), wherein the first channel (C1) connects the downstream side of the first evaporator (11) and the upstream side of the low-stage-side compressor (3), and the first valve unit (21) opens and closes the first channel (C1); a second channel (C2) and a second valve unit (22), wherein the second channel (C2) connects the downstream side of the first evaporator (11) and the upstream side of the high-stage-side compressor (4), and the second valve unit (22) opens and closes the second channel (C2); a third channel (C3) and a third valve section (23), wherein the third channel (C3) connects the downstream side of the second evaporator (12) and the upstream side of the low-stage-side compressor (3), and the third valve section (23) opens and closes the third channel (C3); and a fourth channel (C4) and a fourth valve unit (24), wherein the fourth channel (C4) connects the downstream side of the second evaporator (12) and the upstream side of the high-stage-side compressor (4), and the fourth valve unit (24) opens and closes the fourth channel (C4).

Description

Heat pump

Technical Field

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

The present application claims priority based on japanese patent application No. 2017-215660, filed on 8/11/2017, the contents of which are incorporated herein by reference.

Background

A refrigeration cycle, that is, a heat pump, provided with a refrigerant circuit in which a refrigerant circulates by repeating compression and expansion is known. In such a heat pump, as described in patent document 1, for example, there is a case where the refrigerant is compressed in two stages by a low-stage compressor for compressing the refrigerant and a high-stage compressor for further compressing the refrigerant discharged from the low-stage compressor.

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

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-

Disclosure of Invention

Problems to be solved by the invention

Here, in the heat pump of patent document 1, the refrigerant from the evaporator is introduced into the low-stage-side compressor and then introduced into the high-stage-side compressor.

However, the heat exchange amount of the evaporator is not always constant, and may vary due to environmental factors and the like. Therefore, there are cases where: the temperature of the refrigerant introduced from the heat exchanger to the low-stage-side compressor is not constant, and the refrigerant introduced to the low-stage-side compressor is not in a state optimal for compression by the low-stage-side compressor, so that the heat pump as a whole cannot be operated efficiently.

Accordingly, the present invention provides a heat pump that can achieve efficient operation by introducing a refrigerant in an optimum state for compression into a low-stage compressor and a high-stage compressor.

Means for solving the problems

A heat pump according to a first aspect of the present invention includes: a low-stage side compressor; a high-stage-side compressor connected in series with the low-stage-side compressor on a downstream side of the low-stage-side compressor; a condenser connected to a downstream side of the high-stage-side compressor; an expansion mechanism connected to a downstream side of the condenser; a first evaporator and a second evaporator connected in parallel on a downstream side of the expansion mechanism; a first channel connecting a downstream side of the first evaporator and an upstream side of the low-stage-side compressor, and a first valve section opening and closing the first channel; a second flow path connecting a downstream side of the first evaporator and an upstream side of the high-stage-side compressor, and a second valve section opening and closing the second flow path; a third channel connecting the downstream side of the second evaporator and the upstream side of the low-stage-side compressor, and a third valve section opening and closing the third channel; and a fourth channel connecting the downstream side of the second evaporator and the upstream side of the high-stage-side compressor, and a fourth valve opening and closing the fourth channel.

In this way, the heat pump includes the first evaporator and the second evaporator. That is, the heat pump includes a multi-source type refrigerant circuit having a plurality of heat exchangers having different heat exchange amounts and installation environments.

Here, in each evaporator, the state of the refrigerant heading for the low-stage-side compressor and the high-stage-side compressor may not be optimum for compression by the low-stage-side compressor and the high-stage-side compressor due to a change in the heat exchange amount and a change in the temperature of the refrigerant. Here, by opening and closing the first flow path, the second flow path, the third flow path, and the fourth flow path by the first valve, the second valve, the third valve, and the fourth valve, respectively, it is possible to introduce the refrigerant not only from the first evaporator to the low-stage compressor but also to directly introduce the refrigerant to the high-stage compressor by bypassing the low-stage compressor. In addition, the introduction path of the refrigerant introduced from the second evaporator to the compressor can be switched simultaneously with the switching of the introduction path of the refrigerant introduced from the first evaporator to the compressor. That is, the refrigerant can be introduced not only into the low-stage compressor from the second evaporator but also directly into the high-stage compressor while bypassing the low-stage compressor.

Therefore, the introduction path of the refrigerant into the compressor capable of achieving the optimum compression can be switched according to the state of the refrigerant flowing out from each evaporator.

A heat pump according to a second aspect of the present invention may further include a control unit that controls opening and closing operations of the first valve unit, the second valve unit, the third valve unit, and the fourth valve unit in accordance with a load in the first evaporator and the second evaporator.

By providing such a control unit, it is possible to automatically switch the refrigerant introduction path so that the refrigerant is introduced into the compressor capable of achieving optimum compression, in accordance with the state of the refrigerant flowing out of each evaporator.

In the heat pump according to a third aspect of the present invention, in addition to the second aspect, the control unit may control opening and closing operations of the first valve unit, the second valve unit, the third valve unit, and the fourth valve unit so as to be switchable between a first state in which the refrigerant from the first evaporator is introduced into the low-stage-side compressor and the refrigerant from the second evaporator is directly introduced into the high-stage-side compressor, and a second state in which the refrigerant from the first evaporator is directly introduced into the high-stage-side compressor and the refrigerant from the second evaporator is introduced into the low-stage-side compressor.

According to such a heat pump, the flow of the refrigerant can be switched between the first state and the second state, and therefore, the refrigerant from the first evaporator and the flow of the refrigerant from the second evaporator do not interfere with each other, and the refrigerant can be introduced into the optimum compressor by circulating the refrigerant so that the flow of the refrigerant from the first evaporator and the flow of the refrigerant from the second evaporator intersect with each other. Therefore, the degree of freedom of operation is improved, and efficient operation can be realized.

Effects of the invention

According to the heat pump described above, the refrigerant in the most suitable state for compression can be introduced into the low-stage compressor and the high-stage compressor, and an efficient operation can be achieved.

Drawings

Fig. 1 is an overall configuration diagram of a heat pump according to an embodiment of the present invention.

Fig. 2 is an overall configuration diagram of the heat pump according to the embodiment of the present invention, and shows a case where the refrigerant circulates in the a mode. The portion where the refrigerant does not flow is indicated by a broken line.

Fig. 3 is an overall configuration diagram of the heat pump according to the embodiment of the present invention, and shows a case where the refrigerant circulates in the B mode. The portion where the refrigerant does not flow is indicated by a broken line.

Fig. 4 is an overall configuration diagram of the heat pump according to the embodiment of the present invention, and shows a case where the refrigerant circulates in the C mode. The portion where the refrigerant does not flow is indicated by a broken line.

Fig. 5 is an overall configuration diagram of the heat pump according to the embodiment of the present invention, and shows a case where the refrigerant circulates in the D mode. The portion where the refrigerant does not flow is indicated by a broken line.

Detailed Description

The heat pump 1 according to the embodiment of the present invention will be described below.

As shown in fig. 1, a heat pump 1 of the present embodiment includes a refrigerant circuit 2 that operates in a two-stage compression cycle. The refrigerant circuit 2 includes a low-stage-side compressor 3, a high-stage-side compressor 4, a condenser 5, an expansion valve (expansion mechanism) 6, and an evaporator 10, and these components are connected in sequence by a pipe 15. A refrigerant R such as carbon dioxide is circulated through the refrigerant circuit 2. Here, the refrigerant R is not particularly limited to carbon dioxide.

The low-stage-side compressor 3 sucks the refrigerant R and compresses the refrigerant R.

The high-stage-side compressor 4 is connected in series with the low-stage-side compressor 3, and further compresses the refrigerant R discharged from the low-stage-side compressor 3 to a high pressure.

The condenser 5 exchanges heat between the high-temperature and high-pressure refrigerant R discharged from the high-stage compressor 4 and a heat medium R1 such as air or water, cools and condenses the refrigerant R.

The expansion valve 6 adiabatically expands the refrigerant R from the condenser 5, and decompresses the refrigerant R. The expansion valve 6 is provided in plural (two in the present embodiment) and on the upstream side (inlet side) of the evaporator 10 corresponding to a first evaporator 11 and a second evaporator 12 described later.

In the present embodiment, the evaporator 10 is provided with a first evaporator 11 and a second evaporator 12. The first evaporator 11 is disposed in parallel with the second evaporator 12.

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 (intake side) of the low-stage-side compressor 3 serves as a first flow path C1. The first channel C1 is provided with a first valve portion 21, and the first valve portion 21 opens and closes the first channel C1 such that the refrigerant R can flow or cannot flow through the first channel C1.

A pipe 15 between the first evaporator 11 and the upstream side of the high-stage-side compressor 4 (the intake side of the high-stage-side compressor 4 and the discharge side of the low-stage-side compressor 3) serves as a second flow path C2. The second passage C2 is provided with a second valve unit 22, and the second valve unit 22 opens and closes the second passage C2 such that the refrigerant R can flow or cannot flow through the second passage C2. In the present embodiment, the first flow path C1 is provided so as to branch from the second flow path C2 on the upstream side of the position where the second valve unit 22 is provided, that is, on the side closer to the first evaporator 11.

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-side compressor 3 serves as a third flow path C3. The third flow path C3 is provided with a third valve portion 23, and the third valve portion 23 opens and closes the third flow path C3 such that the refrigerant R can flow or cannot flow through the third flow path C3. In the present embodiment, the first flow path C1 is connected to the third flow path C3 on the downstream side of the position where the third valve portion 23 is provided, that is, on the low-stage-side compressor 3.

A pipe 15 between the second evaporator 12 and the upstream side of the high-stage-side compressor 4 (the intake side of the high-stage-side compressor 4 and the discharge side of the low-stage-side compressor 3) serves as a fourth flow path C4. The fourth flow path C4 is provided with a fourth valve portion 24, and the fourth valve portion 24 opens and closes the fourth flow path C4 such that the refrigerant R can flow or cannot flow through the fourth flow path C4. In the present embodiment, the fourth flow path C4 is provided so as to branch from the third flow path C3 on the upstream side of the position where the third valve portion 23 is provided, that is, on the side closer to the second evaporator 12.

In the present embodiment, the control UNIT 30 is provided, and the control UNIT 30 includes an MPU (MICRO-PROCESSING UNIT) or the like that opens and closes the first valve UNIT 21, the second valve UNIT 22, the third valve UNIT 23, and the fourth valve UNIT 24.

The control unit 30 opens and closes the first valve unit 21, the second valve unit 22, the third valve unit 23, and the fourth valve unit 24 in accordance with the load (heat exchange amount) in the first evaporator 11 and the second evaporator 12.

Next, a control method for controlling the opening and closing operations of the respective valves by the control unit 30 will be described.

Hereinafter, the temperature of the refrigerant R flowing out of the first evaporator 11 is T1, and the temperature of the refrigerant R flowing out of the second evaporator 12 is T2.

[ A mode ]

The case of T1 < T2 is the A mode (first state). In this mode, the control unit 30 closes the second valve unit 22 and opens the first valve unit 21 as shown in fig. 2, so that the refrigerant R from the first evaporator 11 is introduced into the low-stage-side compressor 3. Thus, the refrigerant R from the first evaporator 11 is compressed by the high-stage-side compressor 4 after being compressed by the low-stage-side compressor 3.

In this mode, the control unit 30 closes the third valve unit 23 and opens the fourth valve unit 24 so that the refrigerant R from the second evaporator 12 is introduced only into the high-stage compressor 4 without passing through the low-stage compressor 3. Thus, the refrigerant R from the second evaporator 12 is compressed only by the high-stage-side compressor 4.

[ B mode ]

The case where T1 > T2 is B mode (second state). In this mode, the control unit 30 closes the first valve unit 21 and opens the second valve unit 22 as shown in fig. 3 so that the refrigerant R from the first evaporator 11 is introduced only into the high-stage compressor 4 without passing through the low-stage compressor 3. Therefore, the refrigerant R from the first evaporator 11 is not compressed by the low-stage-side compressor 3 but compressed only by the high-stage-side compressor 4.

In this mode, the control unit 30 closes the fourth valve unit 24 and opens the third valve unit 23 so that the refrigerant R from the second evaporator 12 is introduced into the low-stage-side compressor 3. Thus, the refrigerant R from the second evaporator 12 is compressed by the high-stage-side compressor 4 after being compressed by the low-stage-side compressor 3.

[ C mode ]

And of refrigerant R flowing out of condenser 5The case where the temperature is equal to T1 and T2 is the C mode. In this mode, the control unit 30 stops the operation of the low-stage-side compressor 3 as shown in fig. 4. The control unit 30 closes the first valve unit 21 and the third valve unit 23 and opens the second valve unit 22 and the fourth valve unit 24 so that the refrigerant R flowing out of the first evaporator 11 and the second evaporator 12 is introduced only into the high-stage compressor 4 without passing through the low-stage compressor 3. Therefore, neither the refrigerant R from the first evaporator 11 nor the refrigerant R from the second evaporator 12 is compressed by the low-stage-side compressor 3 but only the high-stage-side compressor 4.

[ D mode ]

And a case where the temperature difference between the refrigerant R flowing out of the condenser 5 and the temperatures of T1 and T2 is large is D mode. In this mode, the control unit 30 closes the second valve unit 22 and the fourth valve unit 24 and opens the first valve unit 21 and the third valve unit 23 so that the refrigerant R flowing out of the first evaporator 11 and the second evaporator 12 is introduced into the low-stage-side compressor 3, as shown in fig. 5. Thus, the refrigerant R from the first evaporator 11 and the refrigerant R from the second evaporator 12 are both compressed by the high-stage-side compressor 4 after being compressed by the low-stage-side compressor 3.

The heat pump 1 of the present embodiment described above includes the first evaporator 11 and the second evaporator 12. That is, the heat pump 1 includes a multi-source type refrigerant circuit 2, and the multi-source type refrigerant circuit 2 includes a plurality of heat exchangers having different heat exchange amounts and installation environments, that is, a first evaporator 11 and a second evaporator 12.

Here, in each evaporator 10, the state of the refrigerant R heading for the low-stage-side compressor 3 and the high-stage-side compressor 4 may not be the most suitable state for compression by the low-stage-side compressor 3 and the high-stage-side compressor 4 due to a change in the temperature of the refrigerant R caused by a change in the load (heat exchange amount). In the present embodiment, the first flow path C1, the second flow path C2, the third flow path C3, and the fourth flow path C4 are opened and closed by the first valve portion 21, the second valve portion 22, the third valve portion 23, and the fourth valve portion 24 by the control portion 30, whereby the refrigerant R can be introduced not only from the first evaporator 11 to the low-stage compressor 3 but also directly to the high-stage compressor 4 by bypassing the low-stage compressor 3.

In addition, the switching of the flow path of the refrigerant R from the first evaporator 11 and the switching of the flow path of the refrigerant R from the second evaporator 12 can be performed. That is, the refrigerant R can be introduced not only from the second evaporator 12 to the low-stage compressor 3 but also directly to the high-stage compressor 4 bypassing the low-stage compressor 3.

Specifically, by operating the first valve unit 21, the second valve unit 22, the third valve unit 23, and the fourth valve unit 24 as in the a mode to the D mode, the introduction path of the refrigerant R into the compressor capable of realizing the optimum compression of the low-stage-side compressor 3 or the high-stage-side compressor 4 can be switched according to the state of the refrigerant R flowing out of each of the evaporators 10(11, 12). Therefore, the refrigerant R in the most suitable state for compression can be introduced into the low-stage-side compressor 3 and the high-stage-side compressor 4, and an efficient operation can be achieved.

Further, by providing the control unit 30, it is possible to automatically switch the introduction path of the refrigerant R into the compressor capable of realizing the optimum compression, out of the low-stage compressor 3 and the high-stage compressor 4, according to the state of the refrigerant R flowing out from the first evaporator 11 and the second evaporator 12, respectively.

Further, by switching the flow of the refrigerant R between the a mode and the B mode, the refrigerant R from the first evaporator 11 can be introduced into either the low-stage-side compressor 3 or the high-stage-side compressor 4, and the refrigerant R from the second evaporator 12 can be introduced into either the low-stage-side compressor 3 or the high-stage-side compressor 4.

That is, the refrigerant R from the first evaporator 11 and the refrigerant R from the second evaporator 12 can flow so that the flow of the refrigerant R from the first evaporator 11 and the flow of the refrigerant R from the second evaporator 12 intersect with each other, and can flow into the low-stage compressor 3 and the high-stage compressor 4, without interfering with each other. Thus, the degree of freedom of operation is improved.

While the embodiments of the present invention have been described above with reference to the drawings, the configurations and combinations thereof in the embodiments are examples, and additions, omissions, substitutions, and other modifications of the configurations can be made without departing from the spirit of the present invention. The present invention is not limited by the embodiments, but is only limited by the claims.

For example, the control unit 30 may not be provided. In this case, the first valve unit 21, the second valve unit 22, the third valve unit 23, and the fourth valve unit 24 can be opened and closed manually.

The number of evaporators 10 may be three or more, and the number of evaporators 10 is not limited to the above.

Industrial applicability

Description of the reference numerals

1 Heat pump

2 refrigerant circuit

3 low-stage side compressor

4 high-stage side compressor

5 condenser

6 expansion valve (expansion mechanism)

10 evaporator

11 first evaporator

12 second evaporator

15 piping

21 first valve part

22 second valve part

23 third valve part

24 fourth valve part

30 control part

R refrigerant

R1, R2 and R3 heat medium

C1 first flow path

C2 second flow path

C3 third flow Path

C4 fourth flow path.

Claims

1. A heat pump in which, in a heat pump,

the heat pump is provided with:

a low-stage side compressor;

a high-stage-side compressor connected in series with the low-stage-side compressor on a downstream side of the low-stage-side compressor;

a condenser connected to a downstream side of the high-stage-side compressor;

an expansion mechanism connected to a downstream side of the condenser;

a first evaporator and a second evaporator connected in parallel on a downstream side of the expansion mechanism;

a first channel connecting a downstream side of the first evaporator and an upstream side of the low-stage-side compressor, and a first valve section opening and closing the first channel;

a second flow path connecting a downstream side of the first evaporator and an upstream side of the high-stage-side compressor, and a second valve section opening and closing the second flow path;

a third channel connecting the downstream side of the second evaporator and the upstream side of the low-stage-side compressor, and a third valve section opening and closing the third channel; and

and a fourth channel connecting the downstream side of the second evaporator and the upstream side of the high-stage-side compressor, and a fourth valve opening and closing the fourth channel.

2. The heat pump of claim 1, wherein,

the heat pump further includes a control unit that controls opening and closing operations of the first valve unit, the second valve unit, the third valve unit, and the fourth valve unit in accordance with a load in the first evaporator and the second evaporator.

3. The heat pump of claim 2, wherein,

the control unit controls opening and closing operations of the first valve unit, the second valve unit, the third valve unit, and the fourth valve unit so as to be switchable between a first state in which the refrigerant from the first evaporator is introduced into the low-stage-side compressor and the refrigerant from the second evaporator is introduced directly into the high-stage-side compressor, and a second state in which the refrigerant from the first evaporator is introduced directly into the high-stage-side compressor and the refrigerant from the second evaporator is introduced into the low-stage-side compressor.