GB2554560A

GB2554560A - Refrigeration apparatus

Info

Publication number: GB2554560A
Application number: GB1715582.1A
Authority: GB
Inventors: Ikeda Takashi
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2015-05-19
Filing date: 2015-05-19
Publication date: 2018-04-04
Anticipated expiration: 2035-05-19
Also published as: JP6463470B2; GB201715582D0; JPWO2016185568A1; GB2554560B; WO2016185568A1

Abstract

This refrigeration apparatus 100 comprises: a first refrigerant circuit 50 which circulates a first refrigerant therethrough; and a second refrigerant circuit 60 which circulates a second refrigerant therethrough. The first refrigerant circuit 50 includes: a first main refrigerant circuit 52 including a first main evaporator 5 of a cascade condenser 18, the first main evaporator 5 heat exchanging the first refrigerant with the second refrigerant so as to evaporate the first refrigerant; and a first sub-refrigerant flow path 54 including a first sub-evaporator 6 of a sub-cool coil 19, the first sub-evaporator 6 being connected in parallel with the first main evaporator 5 and heat exchanging the first refrigerant with the second refrigerant so as to evaporate the first refrigerant. The second refrigerant circuit 60 includes a second main refrigerant circuit 62 which is configured by a second main condenser 8 of the cascade condenser 18 and a second sub-condenser 13 of the sub-cool coil 19 being connected. The second main condenser 8 heat exchanges the second refrigerant with the first refrigerant so as to condense the second refrigerant. The second sub-condenser 13 heat exchanges the second refrigerant condensed by the second main condenser 8 with the first refrigerant and cools the second refrigerant.

Description

(56) Documents Cited:

WO 2014/024838 A1 JP 2012112622 A (58) Field of Search:

INT CL F25B

Other: Jitsuyo Shinan Koho 1922-1996; Jitsuyo Shinan Toroku Koho 1996-2015; Kokai Jitsuyo Shinan Koho 1971-2015; Toroku Jitsuyo Shinan Koho 1994-2015 (71) Applicant(s):

Mitsubishi Electric Corporation (Incorporated in Japan)

7-3 Marunouchi 2-chome, Chiyoda-ku,

Tokyo 100-8310, Japan (72) Inventor(s):

Takashi Ikeda (74) Agent and/or Address for Service:

Mewburn Ellis LLP

City Tower, 40 Basinghall Street, LONDON, Greater London, EC2V 5DE, United Kingdom (54) Title of the Invention: Refrigeration apparatus Abstract Title: Refrigeration apparatus (57) This refrigeration apparatus 100 comprises: a first refrigerant circuit 50 which circulates a first refrigerant therethrough; and a second refrigerant circuit 60 which circulates a second refrigerant therethrough. The first refrigerant circuit 50 includes: a first main refrigerant circuit 52 including a first main evaporator 5 of a cascade condenser 18, the first main evaporator 5 heat exchanging the first refrigerant with the second refrigerant so as to evaporate the first refrigerant; and a first sub-refrigerant flow path 54 including a first sub-evaporator 6 of a sub-cool coil 19, the first sub-evaporator 6 being connected in parallel with the first main evaporator 5 and heat exchanging the first refrigerant with the second refrigerant so as to evaporate the first refrigerant. The second refrigerant circuit 60 includes a second main refrigerant circuit 62 which is configured by a second main condenser 8 of the cascade condenser 18 and a second sub-condenser 13 of the sub-cool coil 19 being connected. The second main condenser 8 heat exchanges the second refrigerant with the first refrigerant so as to condense the second refrigerant. The second sub-condenser 13 heat exchanges the second refrigerant condensed by the second main condenser 8 with the first refrigerant and cools the second refrigerant.

100

¢0

2/3

FI Λ

I lx Z

REFRIGERANT	002	R4I0A	R32	R134a
GWP	-	1	2090	675	1300
CONDENSING TEMPERATURE	°C	25
SUBCOOLING	K	5
EVAPORATION TEMPERATURE.	°C	„10
GAS TEMPERATURE (EVAPORATOR OUTLET)	°C	0
CAPACITY	kW	25.00	25,00	25,00	25,00
INPUT	kW	5,05	3.94	3.95	3.75
COP	“·	4.95	6.34	5.32	6.66

FSf* Ti IVJ. O

A

PRESSURE

ENTHALPY

3/3

LOW-PRESSURE

SIDE PRESSURE; v

TARGET OPERATION PRESSURE VALUE; V1

OPENfNG-AND-CLOSiNG

THRESHOLD VALUE; V2

STOP PRESSURE VALUE; V3

FIG. 5

RETURN

DESCRIPTION

Title of Invention

REFRIGERATION APPARATUS

Technical Field [0001]

The present invention relates to a refrigeration apparatus including a first refrigerant circuit and a second refrigerant circuit.

Background Art [0002]

Conventionally, a dual refrigeration apparatus has been known that exchanges heat between an evaporator of a high-temperature side refrigeration cycle and a condenser of a low-temperature side refrigeration cycle (see Patent Literature 1). Ina dual refrigeration apparatus described in Patent Literature 1, refrigerant in a lowtemperature side refrigeration cycle condensed by a condenser is cooled to a subcooling state by a subcooler.

Citation List

Patent Literature [0003]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 3263555

Summary of Invention

Technical Problem [0004]

However, in the refrigeration apparatus as described in Patent Literature 1, a subcooling coil and a cascade condenser are connected in series in first refrigerant circuit, and a first refrigerant that has cooled a second refrigerant of the second refrigerant circuit by the subcooling coil in the first refrigerant circuit condenses the second refrigerant of the second refrigerant circuit by the cascade condenser. Consequently, in the conventional refrigeration apparatus as described in Patent Literature 1, a saturation temperature of the first refrigerant that cools the second refrigerant of the second refrigerant circuit by the subcooling coil in the first refrigerant circuit becomes higher as compared with a saturation temperature of the first refrigerant that condenses the second refrigerant of the second refrigerant circuit by the cascade condenser.

[0005]

The present invention has been made in view of the above-described problem, and has as an object to provide a refrigeration apparatus that has an improved adjustability of the saturation temperature of the first refrigerant that cools the second refrigerant of the second refrigerant circuit by the subcooling coil and the saturation temperature of the first refrigerant that cools the second refrigerant of the second refrigerant circuit by the cascade condenser in the first refrigerant circuit.

Solution to Problem [0006]

A refrigeration apparatus according to an embodiment of the present invention includes: a first refrigerant circuit circulating a first refrigerant and a second refrigerant circuit circulating a second refrigerant, wherein the first refrigerant circuit includes: a first main refrigerant circuit in which a first compressor compressing the first refrigerant, a first condenser condensing the first refrigerant compressed by the first compressor, a first main expansion device expanding the first refrigerant condensed by the first condenser, and a first main evaporation unit of a cascade condenser, the first main evaporation unit causing the first refrigerant expanded by the first main expansion device to exchange heat with the second refrigerant to evaporate the first refrigerant are connected; and a first sub refrigerant flow path connected in parallel with the first main expansion device and the first main evaporation unit, the first sub refrigerant flow path being provided with a first sub expansion device expanding the first refrigerant condensed by the first condenser and a first sub evaporation unit of a subcooling coil, the first sub evaporation unit causing the first refrigerant expanded by the first sub expansion device to exchange heat with the second refrigerant to evaporate the first refrigerant, and wherein the second refrigerant circuit includes: a second main refrigerant circuit in which a second compressor compressing the second refrigerant, a second main condensing unit of the cascade condenser, the second main condensing unit causing the second refrigerant compressed by the second compressor to exchange heat with the first refrigerant to condense the second refrigerant, and a second sub condensing unit of the subcooling coil, the second sub condensing unit causing the second refrigerant condensed by the second main condensing unit to exchange heat with the first refrigerant to cool the second refrigerant are connected.

Advantageous Effects of Invention [0007]

The aforementioned embodiment of the present invention provides the refrigeration apparatus having an improved adjustability of the saturation temperature of the first refrigerant that cools the second refrigerant of the second refrigerant circuit by the subcooling coil and the saturation temperature of the first refrigerant that cools the second refrigerant of the second refrigerant circuit by the cascade condenser in the first refrigerant circuit.

Brief Description of Drawings [0008] [Fig. 1] Fig. 1 is a diagram schematically describing an example refrigeration apparatus according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a diagram exemplifying refrigerant used in the refrigeration apparatus described in Fig. 1.

[Fig. 3] Fig. 3 is a diagram illustrating an example of operations of a first refrigerant circuit and a second refrigerant circuit described in Fig. 1.

[Fig. 4] Fig. 4 is a diagram illustrating an opening-and-closing threshold value to determine opening and closing of a first opening-and-closing device described in Fig. 1.

[Fig. 5] Fig. 5 is a diagram illustrating an example of operations of the refrigeration apparatus described in Fig. 1.

Description of Embodiments [0009]

Hereinafter, an embodiment according to the present invention will be described in detail with reference to drawings. Note that, same or corresponding parts in the figures are assigned with same reference signs, and descriptions thereof will be appropriately omitted or simplified. Moreover, the shapes, sizes, arrangement and so forth of components described in each figure can be appropriately changed within the scope of the invention.

[0010]

Embodiment 1 [Refrigeration apparatus]

Fig. 1 is a diagram schematically describing an example refrigeration apparatus according to Embodiment 1 of the present invention. As shown in Fig. 1, a refrigeration apparatus 100 of the present embodiment includes a first refrigerant circuit 50 in which a first refrigerant circulates and a second refrigerant circuit 60 in which a second refrigerant circulates, and cools an object of interest by use of, for example, a second evaporator 16 of the second refrigerant circuit 60. Moreover, the refrigeration apparatus 100 includes a pressure detector 20 and a controller 21. The pressure detector 20 detects a low-pressure side pressure v, which is a pressure on a suction side of a second compressor 7 of the second refrigerant circuit 60. The controller 21 includes an analog circuit, a digital circuit, a CPU or a combination of at least two of these, and controls opening and closing of a first opening-and-closing device 11 on the basis of at least a detection result of the pressure detector 20. Note that the controller 21 can also control other components to be described as follows. In Fig. 1, to facilitate understanding of the embodiment, pipes connecting components of the first refrigerant circuit 50 are indicated by solid lines, and pipes connecting components of the second refrigerant circuit 60 are indicated by dotted lines.

[0011] [First refrigerant circuit]

The first refrigerant circuit 50 includes a first main refrigerant circuit 52 and a first sub refrigerant flow path 54. The first main refrigerant circuit 52 includes a first compressor 1, a first condenser 2, a first main expansion device 3 and a first main evaporation unit 5 of a cascade condenser 18 that are connected by piping. The first compressor 1 compresses the first refrigerant. The first compressor 1 is, for example, an inverter compressor controlled by an inverter and can change a capacity (an amount of refrigerant discharged per unit time) by properly varying an operating frequency.

Note that the first compressor 1 may be a constant-rate compressor that is operated at a constant operating frequency. The first condenser 2 condenses the first refrigerant by, for example, performing heat exchange between the first refrigerant flowing through the first condenser 2 and air. The first main expansion device 3 expands the first refrigerant, and is, for example, an electronic expansion valve configured to adjust an opening degree. Alternatively, the first main expansion device 3 may be, for example, a capillary tube. The cascade condenser 18 performs heat exchange between the first refrigerant and the second refrigerant, and includes a first main evaporation unit 5 through which the first refrigerant of the first refrigerant circuit 50 flows and a second main condensing unit 8 through which the second refrigerant of the second refrigerant circuit 60 flows. The first main evaporation unit 5 allows the first refrigerant flowing through the first main evaporation unit 5 to exchange heat with the second refrigerant flowing through the second main condensing unit 8 to evaporate the first refrigerant. [0012]

A first sub refrigerant flow path 54 connects a point between the first condenser 2 and the first main expansion device 3, and a point between the first main evaporation unit 5 and the first compressor 1, and is in parallel with the first main expansion device 3 and the first main evaporation unit 5. The first sub refrigerant flow path 54 is provided with a first sub expansion device 4 and a first sub evaporation unit 6 of a subcooling coil 19. The first sub expansion device 4 expands the first refrigerant, and is, for example, an electronic expansion valve configured to adjust an opening degree. Alternatively, the first sub expansion device 4 may be, for example, a capillary tube. The subcooling coil 19 performs heat exchange between the first refrigerant and the second refrigerant, and includes a first sub evaporation unit 6 through which the first refrigerant of the first refrigerant circuit 50 flows and a second sub condensing unit 13 through which the second refrigerant of the second refrigerant circuit 60 flows. The first sub evaporation unit 6 allows the first refrigerant flowing through the first sub evaporation unit 6 to exchange heat with the second refrigerant flowing through the second sub condensing unit 13 to evaporate the first refrigerant.

[0013] [Second refrigerant circuit]

The second refrigerant circuit 60 includes a second main refrigerant circuit 62, a bypass flow path 64 and an injection flow path 66. The second main refrigerant circuit 62 includes: a second compressor 7; a second main condensing unit 8 of the cascade condenser 18; the first opening-and-closing device 11; a liquid receiver 9; a check valve 12; a second sub condensing unit 13 of the subcooling coil 19; a second opening-andclosing device 14; a second expansion device 15 and a second evaporator 16 that are connected by piping.

[0014]

The second compressor 7 compresses the second refrigerant. The second compressor 7 is, for example, an inverter compressor controlled by an inverter and can change a capacity (an amount of refrigerant discharged per unit time) by properly varying an operating frequency. Note that the second compressor 7 may be a constant-rate compressor that is operated at a constant operating frequency. The second main condensing unit 8 allows the second refrigerant flowing through the second main condensing unit 8 to exchange heat with the first refrigerant flowing through the first main evaporation unit 5 to condense the second refrigerant. The first opening-and-closing device 11 is, for example, a solenoid valve or others to control flow of the second refrigerant by open/close operation. The liquid receiver 9 is, for example, a reservoir that stores refrigerant. The check valve 12 allows refrigerant flowing from the liquid receiver 9 to pass, and prevents the refrigerant from flowing into the liquid receiver 9 by passing through the check valve 12. The second sub condensing unit 13 allows the second refrigerant flowing through the second sub condensing unit 13 to exchange heat with the first refrigerant flowing through the first sub evaporation unit 6 to cool the second refrigerant. The second opening-and-closing device 14 is, for example, a solenoid valve or others to control flow of the second refrigerant by open/close operation. The second expansion device 15 expands the second refrigerant, and is, for example, an electronic expansion valve configured to adjust an opening degree. Alternatively, the second expansion device 15 may be, for example, a capillary tube. The second evaporator 16 evaporates the second refrigerant by, for example, performing heat exchange between the second refrigerant flowing through the second evaporator 16 and air.

[0015]

The bypass flow path 64 connects a point between the second main condensing unit 8 and the first opening-and-closing device 11, and a point between the check valve 12 and the second sub condensing unit 13, and is in parallel with the first opening-andclosing device 11, the liquid receiver 9 and the check valve 12. The injection flow path 66 connects a point between the second sub condensing unit 13 and the second opening-and-closing device 14, and a point between the second evaporator 16 and the second compressor 7, and is in parallel with the second opening-and-closing device 14, the second expansion device 15 and the second evaporator 16. The injection flow path 66 is provided with an injection expansion device 17. The injection expansion device 17 expands the second refrigerant, and is, for example, an electronic expansion valve configured to adjust an opening degree. Alternatively, the second expansion device 15 may be, for example, a capillary tube.

[0016] [Refrigerant]

Fig. 2 is a diagram exemplifying the refrigerant used in the refrigeration apparatus described in Fig. 1. In recent years, in view of dealing with global warming, use of refrigerant having low GWP (global warming potential) has been encouraged. Consequently, in the refrigeration apparatus 100 of the embodiment, a refrigerant having a low GWP is selected to be used for the second refrigerant circuit 60. This is because the second refrigerant circuit 60 described in Fig. 1 includes, for example, an indoor unit (illustration thereof is omitted) unitized by including the second opening-andclosing device 14, the second expansion device 15 and the second evaporator 16 and an outdoor unit (illustration thereof is omitted) unitized by including the second compressor 7, the second main condensing unit 8, the first opening-and-closing device

11, the liquid receiver 9, the check valve 12, the second sub condensing unit 13 and the injection expansion device 17. Connection and construction of the indoor unit and the outdoor unit, illustration of which is omitted, are performed by workers in the field where the refrigeration apparatus 100 is placed. It is known that the refrigerant is liable to leak from the portions connecting the indoor unit and the outdoor unit illustration of which is omitted. Consequently, in the second refrigerant circuit 60 in the example of the embodiment, for instance, CO2 (carbon dioxide) having a low GWP is adopted.

Note that the refrigerant used for the second refrigerant circuit 60 is not limited to CO2; however, the one with a low GWP may be selected.

[0017]

The first refrigerant used for the first refrigerant circuit 50 is selected so as to provide higher efficiency (COP) than that of the second refrigerant circulated in the first refrigerant circuit 50. In other words, under operating conditions of the first refrigerant circuit 50, the first refrigerant provides higher efficiency as compared with the second refrigerant. This is because the unit (illustration thereof is omitted) including the first refrigerant circuit 50 is assembled at a manufacturer (a maker), and therefore, the first refrigerant circuit 50 has been subjected to a test of airtightness or the like and shipped. Since the possibility of leakage of the refrigerant is reduced in the first refrigerant circuit 50 as compared with the second refrigerant circuit 60, it is possible to select a refrigerant providing high efficiency. Note that, preferably, a refrigerant having a low GWP is also selected as the first refrigerant.

[0018]

As described above, in the example of the embodiment, since a refrigerant having a low GWP is used in the second refrigerant circuit 60 that has a possibility of leakage of refrigerant, measures against, for example, global warming are provided. Further, in the example of the embodiment, since a refrigerant providing a high efficiency is used in the first refrigerant circuit 50 in which a possibility of leakage of refrigerant is reduced, the efficiency (COP) of the first refrigerant circuit 50 and an entire refrigeration apparatus 100 is improved.

[0019] [Operations of refrigerant circuit]

Next, an example of operations of the first refrigerant circuit 50 and the second refrigerant circuit 60 will be described. Note that, when the refrigeration apparatus 100 cools an object of interest, that is, when the second evaporator 16 is used for cooling an object of interest, the second opening-and-closing device 14 is brought into an open state to allow the second refrigerant to flow into the second evaporator 16.

[0020]

Fig. 3 is a diagram illustrating an example of operations of the first refrigerant circuit and the second refrigerant circuit described in Fig. 1. First, an example of operations of the first refrigerant circuit 50 shown in Fig. 1 will be described. The first refrigerant compressed by the first compressor 1 comes to the position of the point B in Fig. 3. The first refrigerant compressed by the first compressor 1 in Fig. 1 is subjected to heat exchange in the first condenser 2 to be condensed, and comes to the position of the point C in Fig. 3. The first refrigerant condensed in the first condenser 2 in Fig. 1 branches into the first refrigerant flowing into the first main expansion device 3 and the first refrigerant flowing into the first sub expansion device 4. The first refrigerant flowing into the first main expansion device 3 is expanded by the first main expansion device 3 and comes to the position of the point D in Fig. 3. The first refrigerant expanded by the first main expansion device 3 in Fig. 1 is subjected to heat exchange in the first main evaporation unit 5 to be evaporated and merges with the first refrigerant passed through the first sub evaporation unit 6, and comes to the position of the point A in Fig. 3. Moreover, the first refrigerant flowing into the first sub expansion device 4 in Fig. 1 is expanded by the first sub expansion device 4, and comes to the position of the point D in Fig. 3. The first refrigerant expanded by the first sub expansion device 4 in Fig. 1 is subjected to heat exchange in the first sub evaporation unit 6 to be evaporated and merges with the first refrigerant passed through the first main evaporation unit 5, and comes to the position of the point A in Fig. 3. The first refrigerant at the point A is compressed again in the first compressor 1 in Fig. 1. Note that, by adjusting the opening degree or others of at least one of the first main expansion device 3 and the first sub expansion device 4, it is possible to adjust the flow rate of the first refrigerant flowing through the first main expansion device 3 and the first main evaporation unit 5 and the flow rate of the first refrigerant flowing through the first sub expansion device 4 and the first sub evaporation unit 6.

[0021]

Next, an example of operations of the second refrigerant circuit 60 shown in Fig.

will be described. First, a description will be given of an example of operations of the second refrigerant circuit 60 when the second opening-and-closing device 14 is in the open state and the first opening-and-closing device 11 is in the closed state. The second refrigerant compressed by the second compressor 7 comes to the position of the point F in Fig. 3. The second refrigerant compressed by the second compressor 7 in Fig. 1 is subjected to heat exchange in the second main condensing unit 8 to be condensed, and comes to the position of the point H in Fig. 3. The second refrigerant compressed by the second main condensing unit 8 in Fig. 1 flows through the bypass flow path 64 and is subjected to heat exchange in the second sub condensing unit 13, and comes to the position of the point J in Fig. 3. Note that, as shown in Fig. 1, since the check valve 12 is provided, the second refrigerant that has bypassed the liquid receiver 9 does not flow into the liquid receiver 9. The second refrigerant subjected to heat exchange in the second sub condensing unit 13 passes through the second opening-and-closing device 14 and is expanded in the second expansion device 15, and comes to the position of the point K in Fig. 3. The second refrigerant expanded in the second expansion device 15 in Fig. 1 is subjected to heat exchange in the second evaporator 16 to be evaporated, and comes to the position of the point E in Fig. 3. The second refrigerant at the point E is compressed again in the second compressor 7 in Fig. 1.

[0022]

Next, a description will be given of an example of operations of the second refrigerant circuit 60 when the second opening-and-closing device 14 is in the open state and the first opening-and-closing device 11 is in the open state. Note that, as compared with the case where the first opening-and-closing device 11 is in the closed state, the case where the first opening-and-closing device 11 is in the open state is the same in the points except that the second refrigerant condensed in the second main condensing unit 8 passes through the first opening-and-closing device 11, the liquid receiver 9 and the check valve 12 to flow into the second sub condensing unit 13. Consequently, in the following, descriptions overlapping with the above will be omitted or simplified. The second refrigerant condensed in the second main condensing unit 8 comes to the position of the point H in Fig. 3, and passes through the first opening-andclosing device 11 in Fig. 1 to flow into the liquid receiver 9. The second refrigerant radiates heat in the liquid receiver 9 and comes to the position of the point G in Fig. 3. The second refrigerant from the liquid receiver 9 in Fig. 1 passes through the check valve 12 and is subjected to heat exchange in the second sub condensing unit 13, to come to the position of the point L in Fig. 3.

[0023]

Here, a capacity shown by the second evaporator 16 when the first opening-andclosing device 11 in Fig. 1 is in the open state and a capacity shown by the second evaporator 16 when the first opening-and-closing device 11 in is in the closed state will be compared. The capacity shown by the second evaporator 16 when the first opening-and-closing device 11 is in the open state is obtained by a product of a difference in enthalpy between the point L and the point E in Fig. 3 and a refrigerant circulation amount of the second refrigerant. Moreover, the capacity shown by the second evaporator 16 when the first opening-and-closing device 11 is in the closed state is obtained by a product of a difference in enthalpy between the point K and the point E and a refrigerant circulation amount of the second refrigerant. Accordingly, if the refrigerant circulation amounts of the second refrigerant are equal, the capacity shown by the second evaporator 16 is increased when the second refrigerant is not allowed to flow into the liquid receiver 9 by bringing the first opening-and-closing device 11 into the closed state. This is because heat radiation of the second refrigerant in the liquid receiver 9 is avoided by causing the second refrigerant to flow through the bypass flow path 64. In the embodiment, when the second refrigerant circuit 60 is in the normal operation, the first opening-and-closing device 11 is brought into the closed state to cause the second refrigerant to flow into the bypass flow path 64 for increasing the capacity shown by the second evaporator 16.

[0024]

Note that, in the second refrigerant circuit 60, when the discharge temperature of the second compressor 7 (the point F in Fig. 3) is higher as compared with the normal times, a portion of the second refrigerant subjected to heat exchange in the second sub condensing unit 13 (the point K in Fig. 3) is expanded in the injection expansion device 17 and mixed with the second refrigerant evaporated in the second evaporator 16 to decrease the temperature at the point E in Fig. 3. Due to temperature drop at the point E in Fig. 3, it is possible to decrease the discharge temperature of the second compressor 7 (the point F in Fig. 3).

[0025]

Moreover, in the example of the embodiment, when it becomes unnecessary to cool the object of interest by the refrigeration apparatus 100, that is, when it becomes unnecessary to carry out cooling by use of the second evaporator 16, the second opening-and-closing device 14 is brought into the closed state. When the second opening-and-closing device 14 is brought into the closed state, the pressure on the lowpressure side of the second compressor 7 from the second opening-and-closing device 14 to the second compressor 7 is reduced. When the pressure on the low-pressure side of the second compressor 7 is reduced to a set pressure that has been set in advance, the second compressor 7 stops operations thereof. Here, when the second opening-and-closing device 14 is brought into the closed state, since the second refrigerant on the low-pressure side of the second refrigerant circuit 60 moves to the high-pressure side of the second refrigerant circuit, there exists excessive refrigerant on the high-pressure side of the second refrigerant circuit, and accordingly, a protective function (illustration thereof is omitted) on the ground of pressure abnormality is performed, or there is a possibility to cause failure. Therefore, when cooling by use of the second evaporator 16 becomes unnecessary, the first opening-and-closing device 11 is brought into the open state to accumulate the second refrigerant in the liquid receiver 9. In the refrigeration apparatus 100 of the embodiment, the second refrigerant circuit 60 includes, for example, an indoor unit (illustration thereof is omitted) unitized by including the second opening-and-closing device 14, the second expansion device 15 and the second evaporator 16 and an outdoor unit (illustration thereof is omitted) unitized by including the second compressor 7, the second main condensing unit 8, the first opening-and-closing device 11, the liquid receiver 9, the check valve 12, the second sub condensing unit 13 and the injection expansion device 17, and the indoor unit and the outdoor unit are independently controlled. As will be described below, by controlling opening and closing of the first opening-and-closing device 11 by use of the pressure on the low-pressure side of the second compressor 7 to accumulate the second refrigerant in the liquid receiver 9, it is possible to prevent the second refrigerant circuit 60 from going into an abnormal state on the outdoor unit side, illustration of which is omitted.

[0026]

Fig. 4 is a diagram illustrating an opening-and-closing threshold value to determine opening and closing of the first opening-and-closing device described in Fig.

1. As shown in Fig. 4, opening and closing of the first opening-and-closing device 11 is determined on the basis of the low-pressure side pressure v on the low-pressure side of the second compressor 7. An opening-and-closing threshold value V2 for determining opening and closing of the first opening-and-closing device 11 is set between a target operation pressure value V1 that is a low-pressure side pressure v that is a target of the second compressor 7 during the normal operation and a stop pressure value V3 that is a low-pressure side pressure v to stop the second compressor 7. This is because, when the second evaporator 16 is used for cooling an object of interest, the second opening-and-closing device 14 is in the open state, and the second compressor 7 is controlled to bring the low-pressure side pressure v close to the target operation pressure value V1 to cause the second compressor 7 to cool the object of interest to a target temperature. Consequently, when it is estimated that the second compressor 7 is controlled to bring the low-pressure side pressure v close to the target operation pressure value V1, it is determined that the second opening-and-closing device 14 is in the open state, and thereby the first opening-and-closing device 11 is closed. By bringing the first opening-and-closing device 11 into the closed state, the second refrigerant does not flow into the liquid receiver 9, but flows through the bypass flow path 64; therefore, the capacity of the second evaporator 16 is increased. Moreover, when cooling by use ofthe second evaporator 16 becomes unnecessary, since the second opening-and-closing device 14 is brought into the closed state, the low-pressure side pressure v is decreased. Therefore, when the low-pressure side pressure v is decreased to the opening-and-closing threshold value V2, by which it is estimated that the second opening-and-closing device 14 is brought into the closed state, or less, the first opening-and-closing device 11 is brought into the open state to accumulate the second refrigerant in the liquid receiver 9.

[0027]

Fig. 5 is a diagram illustrating an example of operations of the refrigeration apparatus described in Fig. 1. In step S1 in Fig. 5, it is determined whether or not the second compressor 7 is in operation. When the second compressor 7 is determined to be in operation in step S1, the process proceeds to step S2. In step S2, the lowpressure side pressure v of the second compressor 7 is obtained and it is determined whether or not the low-pressure side pressure v of the second compressor 7 is not more than the opening-and-closing threshold value V2. When the low-pressure side pressure v of the second compressor 7 is not more than the opening-and-closing threshold value V2 in step S2, the first opening-and-closing device 11 is brought into the open state in step S3. When the low-pressure side pressure v of the second compressor 7 is more than the opening-and-closing threshold value V2 in step S2, the first opening-and-closing device 11 is brought into the closed state in step S4.

Moreover, when the second compressor 7 is determined to be not in operation in step S1, the first opening-and-closing device 11 is brought into the open state in step S5. [0028]

As described above, the refrigeration apparatus 100 ofthe embodiment includes the first refrigerant circuit 50 circulating the first refrigerant, and the second refrigerant circuit 60 circulating the second refrigerant. The first refrigerant circuit 50 includes the first main refrigerant circuit 52 in which the first compressor 1 compressing the first refrigerant, the first condenser 2 condensing the first refrigerant compressed by the first compressor 1, the first main expansion device 3 expanding the first refrigerant condensed by the first condenser 2, and the first main evaporation unit 5 of the cascade condenser 18 causing the first refrigerant to be subjected to heat exchange with the second refrigerant to evaporate the first refrigerant are connected, and the first sub refrigerant flow path 54 connected in parallel with the first main expansion device 3 and the first main evaporation unit 5, in which the first sub expansion device 4 expanding the first refrigerant condensed by the first condenser 2 and the first sub evaporation unit 6 of the subcooling coil 19 causing the first refrigerant expanded by the first sub expansion device 4 to be subjected to heat exchange with the second refrigerant to evaporate the first refrigerant are provided, The second refrigerant circuit 60 includes the second main refrigerant circuit 62 in which the second compressor 7 compressing the second refrigerant, the second main condensing unit 8 of the cascade condenser 18 causing the second refrigerant compressed by the second compressor 7 to be subjected to heat exchange with the first refrigerant to condense the second refrigerant, and the second sub condensing unit 13 of the subcooling coil 19 causing the second refrigerant condensed by the second main condensing unit 8 to be subjected to heat exchange with the first refrigerant to cool the second refrigerant are connected. In the refrigeration apparatus 100 of the embodiment, since the first main evaporation unit 5 of the cascade condenser 18 and the first sub evaporation unit 6 of the subcooling coil 19 are connected in parallel in the first refrigerant circuit 50, adjustability of the saturation temperature of the first refrigerant flowing through the first main evaporation unit 5 and the saturation temperature of the first refrigerant flowing through the first sub evaporation unit 6 is improved. For instance, in the example of the embodiment, efficiency of the refrigeration apparatus 100 is improved by adjusting the saturation temperature of the first refrigerant flowing through the first sub evaporation unit 6 to be not more than the saturation temperature of the first refrigerant flowing through the first main evaporation unit 5.

[0029]

The second main refrigerant circuit 62 of the refrigeration apparatus 100 of the embodiment further includes the first opening-and-closing device 11 controlling a flow of the second refrigerant condensed by the second main condensing unit 8, the liquid receiver 9 accumulating the second refrigerant passed through the first opening-andclosing device 11, and the second opening-and-closing device 14 controlling a flow of the second refrigerant cooled by the second sub condensing unit 13. The second refrigerant circuit 60 includes the bypass flow path 64 connected in parallel with the first opening-and-closing device 11 and the liquid receiver 9. Moreover, the refrigeration apparatus 100 of the embodiment further includes the pressure detector 20 detecting the low-pressure side pressure v on the suction side of the second compressor 7, and the controller 21 controlling opening and closing of the first opening-and-closing device 11 on the basis of the low-pressure side pressure v detected by the pressure detector 20, and, on the basis of the low-pressure side pressure v, the controller 21 brings the first opening-and-closing device 11 into the closed state when the second opening-andclosing device 14 is determined to be in the open state, and brings the first openingand-closing device 11 into the open state when the second opening-and-closing device 14 is determined to be in the closed state. In the refrigeration apparatus 100 of the embodiment, when the second opening-and-closing device 14 is in the open state, the first opening-and-closing device 11 is brought into the closed state to flow the second refrigerant into the bypass flow path 64, and thereby the capacity shown by the second evaporator 16 can be increased. Moreover, in the refrigeration apparatus 100 of the embodiment, when the second opening-and-closing device 14 is in the closed state, the first opening-and-closing device 11 is brought into the open state to accumulate the second refrigerant in the liquid receiver 9, and thereby the second refrigerant circuit 60 can be prevented from going into the abnormal state.

[0030]

The present invention is not limited to the embodiment described above and can be varied within the scope of the invention. In other words, the configuration of the above-described embodiment can be appropriately modified, or at least a part thereof may be substituted by another configuration. Further, the constituents not referred to about disposition thereof can be, not limited to the disposition disclosed in the embodiment, disposed at positions where functions thereof can be achieved.

[0031]

For example, in the above, an example of the dual refrigeration apparatus including the first refrigerant circuit 50 and the second refrigerant circuit 60 was described with reference to Fig. 1; however, the present invention can also be applied to a multiplex refrigeration apparatus including three or more refrigerant circuits.

Reference Signs List [0032] first compressor 2 first condenser 3 first main expansion device 4 first sub expansion device 5 first main evaporation unit 6 first sub evaporation unit 7 second compressor 8 second main condensing unit liquid receiver 11 first opening-and-closing device 12 checkvalve 13 second sub condensing unit 14 second opening-and-closing device 15 second expansion device 16 second evaporator 17 injection expansion device cascade condenser 19 subcooling coil 20 pressure detector controller 50 first refrigerant circuit 52 first main refrigerant circuit first sub refrigerant flow path 60 second refrigerant circuit 62 second main refrigerant circuit 64 bypass flow path 66 injection flow path 100 refrigeration apparatus V1 target operation pressure value V2 opening-andclosing threshold value V3 stop pressure value v low-pressure side pressure

Claims

CLAIMS [Claim 1]

A refrigeration apparatus comprising:

a first refrigerant circuit configured to circulate a first refrigerant and a second refrigerant circuit configured to circulate a second refrigerant, the first refrigerant circuit including a first main refrigerant circuit in which a first compressor configured to compress the first refrigerant, a first condenser configured to condense the first refrigerant compressed by the first compressor, a first main expansion device configured to expand the first refrigerant condensed by the first condenser and a first main evaporation unit of a cascade condenser, the first main evaporation unit being configured to allow the first refrigerant expanded by the first main expansion device to exchange heat with the second refrigerant to evaporate the first refrigerant are connected, and a first sub refrigerant flow path connected in parallel with the first main expansion device and the first main evaporation unit, the first sub refrigerant flow path being provided with a first sub expansion device configured to expand the first refrigerant condensed by the first condenser and a first sub evaporation unit of a subcooling coil, the first sub evaporation unit being configured to allow the first refrigerant expanded by the first sub expansion device to exchange heat with the second refrigerant to evaporate the first refrigerant, the second refrigerant circuit including a second main refrigerant circuit in which a second compressor configured to compress the second refrigerant, a second main condensing unit of the cascade condenser, the second main condensing unit being configured to allow the second refrigerant compressed by the second compressor to exchange heat with the first refrigerant to condense the second refrigerant and a second sub condensing unit of the subcooling coil, the second sub condensing unit being configured to allow the second refrigerant condensed by the second main condensing unit to exchange heat with the first refrigerant to cool the second refrigerant are connected.
[Claim 2]

The refrigeration apparatus of claim 1, wherein the second main refrigerant circuit further includes a first opening-and-closing device configured to control a flow of the second refrigerant condensed by the second main condensing unit, a liquid receiver accumulating the second refrigerant passed through the first opening-and-closing device and a second opening-and-closing device configured to control a flow of the second refrigerant cooled by the second sub condensing unit, and the second refrigerant circuit further includes a bypass flow path connected in parallel with the first opening-and-closing device and the liquid receiver.
[Claim 3]

The refrigeration apparatus of claim 2, further comprising: a pressure detector configured to detect a low-pressure side pressure on a suction side of the second compressor; and a controller configured to control opening and closing of the first opening-andclosing device based on the low-pressure side pressure detected by the pressure detector, wherein, based on the low-pressure side pressure, the controller is configured to control the first opening-and-closing device to be in a closed state when the second openingand-closing device is determined to be in an open state, and control the first openingand-closing device to be in an open state when the second opening-and-closing device is determined to be in a closed state.
[Claim 4]

The refrigeration apparatus of any one of claims 1 to 3, wherein the first refrigerant is selected so as to provide higher efficiency (COP) than that of the second refrigerant circulated in the first refrigerant circuit.