EP3922928A1

EP3922928A1 - Outdoor unit of refrigeration device and refrigeration device comprising same

Info

Publication number: EP3922928A1
Application number: EP19914434.6A
Authority: EP
Inventors: Tomotaka Ishikawa; Nobuya ISHIHARA
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2019-02-05
Filing date: 2019-02-05
Publication date: 2021-12-15
Also published as: WO2020161803A1; JPWO2020161803A1; JP7105933B2; EP3922928A4; CN113348333B; CN113348333A

Abstract

A refrigeration apparatus (100) includes an outdoor unit (101) and an indoor unit (102). The outdoor unit (101) includes a first compressor (1), a second heat exchanger (2), a four-way valve (7), and a refrigerant amount adjustment mechanism (10). In a refrigeration mode, the four-way valve (7) connects the first compressor (1) so that a first refrigerant flows in a normal direction in which the first refrigerant flows toward a first expansion valve (3) via the first compressor (1) and the second heat exchanger (2). In a defrosting mode, the four-way valve (7) connects the first compressor (1) so that the first refrigerant flows in a reverse direction in which the first refrigerant flows from the first compressor (1) to the first heat exchanger (4) and returns from the first expansion valve (3) to the first compressor (1) via the second heat exchanger (2). The refrigerant amount adjustment mechanism (10) is configured to adjust a circulation amount of the first refrigerant in the defrosting mode.

Description

TECHNICAL FIELD

The present disclosure relates to an outdoor unit of a refrigeration apparatus and a refrigeration apparatus including the same.

BACKGROUND ART

A defrosting mode for melting frost formed on a cooler is provided in a refrigeration apparatus. A known defrosting system is, for example, a reverse hot gas defrosting system that changes a direction of circulation of refrigerant using a four-way valve so as to send high-temperature gas from a compressor to the cooler that normally functions as an evaporator.
Japanese Patent No. 5595245 (PTL 1) discloses a refrigeration apparatus that performs defrosting by the reverse hot gas defrosting system in a low-temperature cycle of a binary cycle device.

CITATION LIST

PATENT LITERATURE

PTL 1: Japanese Patent No. 5595245

SUMMARY OF INVENTION

TECHNICAL PROBLEM

The refrigeration apparatus disclosed in Japanese Patent No. 5595245 (PTL 1) can suppress a rise of a high pressure during defrosting through cooling by a cascade condenser that performs heat exchange between refrigerant with high-temperature cycle and refrigerant with low-temperature cycle.
Commonly used as a binary-cycle cascade condenser is a plate heat exchanger. The plate heat exchanger has a small internal volume. Even when condensation of refrigerant is facilitated during defrosting by the cascade condenser, thus, a pressure suppression effect is limited. When melting of frost formed on an evaporator is complete during a defrosting operation with a fan stopped, the refrigerant may not be cooled sufficiently, and a refrigerant pressure may rapidly increase to a design upper limit pressure, which may automatically stop the operation for protection. Not only in a binary cycle device but also in a normal refrigeration cycle apparatus, a situation in which a refrigerant pressure increases rapidly during a defrosting operation is desirably avoided because the design upper limit pressure can be relatively low.
The present disclosure has been made to solve the above problem, and therefore has an object to provide a refrigeration apparatus that is able to suppress a rise of a refrigerant pressure during a defrosting operation.

SOLUTION TO PROBLEM

The present disclosure relates to an outdoor unit of a refrigeration apparatus having a refrigeration mode and a defrosting mode. The outdoor unit includes a first compressor, a second heat exchanger, a four-way valve, and a refrigerant amount adjustment mechanism. The first compressor and the second heat exchanger are connected so that a first refrigerant circulates among the first compressor, the second heat exchanger, and an indoor unit in which a first expansion valve and a first heat exchanger are connected in series. The four-way valve interchanges a connection destination of a discharging port and a connection destination of a suction port of the first compressor so that in the refrigeration mode, the first refrigerant flows in a normal direction in which the first refrigerant flows toward the first expansion valve via the first compressor and the second heat exchanger, and in the defrosting mode, the first refrigerant flows in a reverse direction in which the first refrigerant flows from the first compressor to the first heat exchanger and returns from the first expansion valve to the first compressor via the second heat exchanger. The refrigerant amount adjustment mechanism adjusts a circulation amount of the first refrigerant in the defrosting mode.

ADVANTAGEOUS EFFECTS OF INVENTION

The refrigeration apparatus according to the present disclosure can adjust a circulation amount of the first refrigerant during operation in the defrosting mode, and accordingly, can keep a refrigerant pressure within an appropriate range during operation in the defrosting mode.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 shows a configuration of a refrigeration apparatus according to Embodiment 1.
Fig. 2 shows a configuration of a controller 50 that controls the refrigeration apparatus.
Fig. 3 shows a refrigerant flow in a defrosting mode of the refrigeration apparatus of Embodiment 1.
Fig. 4 is a flowchart for illustrating control performed by the controller in Embodiment 1.
Fig. 5 shows a configuration of a refrigeration apparatus according to Embodiment 2.
Fig. 6 shows a refrigerant flow in a defrosting mode of the refrigeration apparatus of Embodiment 2.
Fig. 7 shows a configuration of a refrigeration apparatus according to Embodiment 3.
Fig. 8 shows a configuration of a refrigeration apparatus according to Embodiment 4.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described below in detail with reference to the drawings. Although several embodiments will be described below, an appropriate combination of the configurations described in the respective embodiments has been intended at the time of application. The same or corresponding parts will be designated by the same reference numerals, and a description thereof will not be repeated.

Embodiment 1

Fig. 1 shows a configuration of a refrigeration apparatus according to Embodiment 1. Referring to Fig. 1, a refrigeration apparatus 100 includes an outdoor unit 101, an indoor unit 102, and pipes 27, 31, which connect outdoor unit 101 with indoor unit 102.
Indoor unit 102 includes a first expansion valve 3 and a first heat exchanger 4. First expansion valve 3 and first heat exchanger 4 are connected in series. First expansion valve 3 may be, for example, a temperature expansion valve controlled based on a temperature of a refrigerant outlet of first heat exchanger 4.
Outdoor unit 101 includes a first compressor 1, a second heat exchanger 2, a four-way valve 7, a refrigerant amount adjustment mechanism 10, and a controller 50.
Fig. 2 shows a configuration of controller 50 that controls the refrigeration apparatus. Referring to Fig. 2, controller 50 includes a processor 51, a memory 52, and a communication interface (not shown), and the like. Processor 51 controls, for example, an operation frequency of first compressor 1 and connection of four-way valve 7 in accordance with data stored in memory 52 and information obtained via the communication interface.
Memory 52 includes, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory. The flash memory stores an operating system, an application program, and various pieces of data. Controller 50 shown in Fig. 1 is implemented by processor 51 executing the operating system and the application program stored in memory 52. The various pieces of data stored in memory 52 are referred to in the execution of the application program.
Referring again to Fig. 1, first compressor 1 and second heat exchanger 2 are connected so that a first refrigerant circulates among first compressor 1, second heat exchanger 2, and indoor unit 102.
Refrigeration apparatus 100 has a refrigeration mode and a defrosting mode as operation modes. In the refrigeration mode, refrigerant flows in a direction indicated by the arrows of Fig. 1. Fig. 3 shows a refrigerant flow in the defrosting mode of the refrigeration apparatus of Embodiment 1.
Four-way valve 7 interchanges a connection destination of a discharging port of first compressor 1 and a connection destination of a suction port of first compressor 1 between the refrigeration mode and the defrosting mode. In the refrigeration mode shown in Fig. 1, four-way valve 7 connects first compressor 1 so that the first refrigerant flows in a normal direction in which the first refrigerant flows toward first expansion valve 3 via first compressor 1 and second heat exchanger 2. In the defrosting mode shown in Fig. 3, four-way valve 7 connects first compressor 1 so that the first refrigerant flows in a reverse direction in which the first refrigerant flows from first compressor 1 to first heat exchanger 4 and returns from first expansion valve 3 to first compressor 1 via second heat exchanger 2.
Refrigerant amount adjustment mechanism 10 is configured to adjust a circulation amount of the first refrigerant in the defrosting mode.
Refrigerant amount adjustment mechanism 10 includes a liquid receiver 8, refrigerant exhaust pipes 34, 35, and a flow regulating valve 45. Liquid receiver 8 is placed between second heat exchanger 2 and first expansion valve 3. Refrigerant exhaust pipes 34, 35 connect an outlet of liquid receiver 8 with a suction port of first compressor 1. Flow regulating valve 45 adjusts a flow rate of the first refrigerant that flows through refrigerant exhaust pipes 34, 35.
Outdoor unit 101 further includes bypass flow paths 36, 37 through which the first refrigerant flows from first expansion valve 3 toward second heat exchanger 2 without passing through liquid receiver 8 in the defrosting mode shown in Fig. 3.
Outdoor unit 101 further includes a second expansion valve 46, which is provided in bypass flow paths 36, 37, and a check valve 43, which is provided in bypass flow path 37 and restricts flowing of the refrigerant flows to a direction from second expansion valve 46 toward second heat exchanger 2.
When four-way valve 7 is switched to the state shown in Fig. 3, check valves 41 to 43 cause the refrigerant to circulate in the direction indicated by the arrows of Fig. 3. In a switch from the refrigeration mode to the defrosting mode, a sufficient amount of refrigerant is stored in liquid receiver 8 of refrigerant amount adjustment mechanism 10. In the defrosting mode, an amount of refrigerant which circulates is added when flow regulating valve 45 is opened. In order to set an amount of refrigerant that circulates in the defrosting mode to an appropriate amount, thus, it suffices that flow regulating valve 45 is closed once the amount of refrigerant reaches the appropriate amount. Since check valve 42 is provided between pipe 25 and pipe 26 after a branch of refrigerant exhaust pipe 34, the refrigerant from first expansion valve 3 will not flow backward to the liquid receiver 8 side even when flow regulating valve 45 is opened in the defrosting mode.
Fig. 4 is a flowchart for illustrating control performed by the controller in Embodiment 1. The process in this flowchart is repeatedly performed every time a certain period of time elapses or every time a predetermined condition is satisfied during operation of the refrigeration apparatus. For example, in the case where defrosting is performed per certain period of time, controller 50 performs the process of the flowchart of Fig. 4 when a certain period of time elapses from the last defrosting of first heat exchanger 4. Note that this shift to the defrosting mode may be determined based on a refrigerant temperature or a state of formation of frost on first heat exchanger 4, which has been detected.
Referring to Fig. 4, when a condition for switching to the defrosting mode is satisfied, controller 50 switches four-way valve 7 from the state of Fig. 1 to the state of Fig. 3 at step S1.
At step S2, controller 50 then monitors outputs of temperature sensor 61 and pressure sensor 62 and determines whether a degree of supercooling (SC: subcooling) of the first refrigerant in bypass flow path 36 in front of second expansion valve 46 is lower than a determination value.
When the SC is less than the determination value (YES at S2), controller 50 opens flow regulating valve 45 to add an amount of refrigerant for circulation. In contrast, when the SC is not less than the determination value (NO at S2), the amount of refrigerant for circulation is sufficient, and accordingly, controller 50 closes flow regulating valve 45.
The process of steps S2 to S4 is repeated until it is determined that defrosting is complete at step S5. Consequently, an amount of refrigerant for circulation in the defrosting mode is adjusted to an appropriate amount.
When it is determined that defrosting is complete (YES at S5), controller 50 returns four-way valve 7 to the state of the refrigeration mode of Fig. 1 at step S6.
Refrigeration apparatus 100 described in Embodiment 1 can appropriately maintain the refrigerant circulation amount during defrosting, and accordingly, can avoid a decrease in defrosting ability and an excessive rise of high pressure due to a shortage of refrigerant. As a result, frost can be reliably melted in a short period of time, and a design pressure can be kept low.

Embodiment 2

Fig. 5 shows a configuration of a refrigeration apparatus according to Embodiment 2. Referring to Fig. 5, a refrigeration apparatus 200 includes an outdoor unit 201, an indoor unit 202, and pipes 27, 31, which connect outdoor unit 201 with indoor unit 202.
Indoor unit 202 has a configuration similar to that of indoor unit 102 of Embodiment 1.
Outdoor unit 201 includes a first refrigeration cycle device 207 on a low temperature side as outdoor unit 101 of Embodiment 1, and further includes a third heat exchanger 214, a second refrigeration cycle device 206 on a high temperature side, and a controller 250 in place of controller 50. For example, a first refrigerant used in first refrigeration cycle device 207 is CO₂ or the like, and a second refrigerant used in second refrigeration cycle device 206 is CO₂, propane, or the like. The other components of outdoor unit 201 are common with those of outdoor unit 101 of Fig. 1, which will not be described repeatedly. Components of controller 250 are also similar to those of controller 50 shown in Fig. 2, which will not be described repeatedly.
Second refrigeration cycle device 206 is configured so that the second refrigerant circulates in order of second compressor 211, fourth heat exchanger 212, third expansion valve 213, and third heat exchanger 214. In the refrigeration mode, third heat exchanger 214 performs heat exchange between the second refrigerant and the first refrigerant which is discharged from second heat exchanger 2 and flows into liquid receiver 8. The refrigerant which flows into liquid receiver 8 is cooled by third heat exchanger 214, and accordingly, a rise of pressure in liquid receiver 8 is suppressed.
First compressor 1 and second heat exchanger 2 are connected so that the first refrigerant circulates among first compressor 1, second heat exchanger 2, and indoor unit 202.
Refrigeration apparatus 200 has a refrigeration mode and a defrosting mode as operation modes. In the refrigeration mode, refrigerant flows in a direction indicated by the arrows of Fig. 5. Fig. 6 shows a refrigerant flow in the defrosting mode of the refrigeration apparatus of Embodiment 2.
A difference in the direction of circulation of refrigerant between the refrigeration mode and the defrosting mode in Embodiment 2 is basically the same as that of Embodiment 1 described with reference to Figs. 1 and 3. Also, control of adjusting an amount of refrigerant is common with that of the flowchart shown in Fig. 4. Thus, the above will not be described repeatedly.
In the case of a binary cycle including second refrigeration cycle device 206 on the high temperature side and first refrigeration cycle device 207 on the low temperature side as described in Embodiment 2, a design pressure of first refrigeration cycle device 207 on the low temperature side is set to be low. Accordingly, adjustment of a refrigerant circulation amount in the defrosting mode by refrigerant amount adjustment mechanism 10 is effective for suppressing a pressure of first refrigeration cycle device 207 on the low temperature side, and is beneficial to the application of carbonic acid gas or the like as the second refrigerant.

Embodiment 3

Fig. 7 shows a configuration of a refrigeration apparatus according to Embodiment 3. Referring to Fig. 7, a refrigeration apparatus 300 includes an outdoor unit 301, an indoor unit 302, and pipes 27, 31, which connect outdoor unit 301 with indoor unit 302.
Indoor unit 302 has a configuration similar to that of indoor unit 202 of

Embodiment 2.

Outdoor unit 301 further includes a fifth heat exchanger 310 in addition to the components of outdoor unit 201 of Embodiment 2. Fifth heat exchanger 310 is configured to, in the defrosting mode, perform heat exchange between a first refrigerant which is discharged from liquid receiver 8 and the first refrigerant which flows through refrigerant exhaust pipe 35.
The other components of outdoor unit 301 are common with those of outdoor unit 201 of Fig. 5, which will not be described repeatedly.
A difference in the direction of circulation of refrigerant between the refrigeration mode and the defrosting mode in Embodiment 3 is basically the same as those of Embodiment 1 described with reference to Figs. 1 to 3 and Embodiment 2 described with reference to Figs. 5 and 6. Control of adjusting an amount of refrigerant is also common with that of the flowchart shown in Fig. 4. Accordingly, the above will not be described repeatedly.
Refrigeration apparatus 300 described in Embodiment 3 liquefies refrigerant which flows into flow regulating valve 45 by fifth heat exchanger 310, in addition to the effect achieved by refrigeration apparatus 200 described in Embodiment 2, and thus, can prevent a decrease in flow rate caused by gaseous refrigerant flowing into flow regulating valve 45. This further achieves an effect that the adjustment of an amount of refrigerant in the defrosting mode is complete early.

Embodiment 4

Fig. 8 shows a configuration of a refrigeration apparatus according to Embodiment 4. Referring to Fig. 8, a refrigeration apparatus 400 includes an outdoor unit 401, an indoor unit 402, and pipes 27, 31, which connect outdoor unit 401 with indoor unit 402.
Indoor unit 402 has a configuration similar to that of indoor unit 202 of Embodiment 2.
Outdoor unit 401 further includes a circulation flow path 410, which connects an inlet of a first refrigerant of third heat exchanger 214 with an outlet of the first refrigerant of liquid receiver 8 and circulates the first refrigerant between third heat exchanger 214 and liquid receiver 8, and a solenoid valve 411, which is provided in circulation flow path 410, in addition to the components of outdoor unit 201 of Embodiment 2.
As described above, circulation flow path 410 is provided and solenoid valve 411 is opened during the defrosting mode, and thus, circulation of the first refrigerant occurs, in which the first refrigerant cooled and liquefied by the third heat exchanger moves to liquid receiver 8 and warm refrigerant of liquid receiver 8 moves to the third heat exchanger and is cooled.
Consequently, a temperature of the refrigerant of liquid receiver 8 is kept low during the defrosting mode, and accordingly, as the defrosting mode is returned to the refrigeration mode, cooling at low temperature in indoor unit 402 can be restarted immediately.
The embodiments disclosed herein have been presented for the purpose of illustration and non-restrictive in every respect. It is therefore intended that the scope of the present disclosure is defined by claims, not only by the embodiments described above, and encompasses all modifications and variations equivalent in meaning and scope to the claims.

REFERENCE SIGNS LIST

1 first compressor; 2 second heat exchanger; 3 first expansion valve; 4 first heat exchanger; 7 four-way valve; 8 liquid receiver; 10 refrigerant amount adjustment mechanism; 25-27, 31 pipe; 34, 35 refrigerant exhaust pipe; 36, 37, 410 flow path; 41-43 check valve; 45 flow regulating valve; 46 second expansion valve; 50, 250 controller; 51 processor; 52 memory; 61 temperature sensor; 62 pressure sensor; 100, 200, 300, 400 refrigeration apparatus; 101, 201, 301, 401 outdoor unit; 102, 202, 302, 402 indoor unit; 206 second refrigeration cycle device; 207 first refrigeration cycle device; 211 second compressor; 212 fourth heat exchanger; 213 third expansion valve; 214 third heat exchanger; 310 fifth heat exchanger; 411 solenoid valve.

Claims

An outdoor unit of a refrigeration apparatus having a refrigeration mode and a defrosting mode, the outdoor unit comprising:
a first compressor and a second heat exchanger connected so that a first refrigerant circulates among the first compressor, the second heat exchanger, and an indoor unit, a first expansion valve and a first heat exchanger being connected in series in the indoor unit;

a four-way valve configured to interchange a connection destination of a discharging port and a connection destination of a suction port of the first compressor so that
in the refrigeration mode, the first refrigerant flows in a normal direction in which the first refrigerant flows toward the first expansion valve via the first compressor and the second heat exchanger, and

in the defrosting mode, the first refrigerant flows in a reverse direction in which the first refrigerant flows from the first compressor to the first heat exchanger and returns from the first expansion valve to the first compressor via the second heat exchanger; and

a refrigerant amount adjustment mechanism configured to adjust a circulation amount of the first refrigerant in the defrosting mode.
The outdoor unit according to claim 1, wherein
the refrigerant amount adjustment mechanism includes
a liquid receiver connected between the second heat exchanger and the first expansion valve,

a refrigerant exhaust pipe connecting an outlet of the liquid receiver with the suction port of the first compressor, and

a flow regulating valve configured to adjust a flow rate of the first refrigerant flowing through the refrigerant exhaust pipe, and

the outdoor unit further comprises a bypass flow path through which the first refrigerant flows from the first expansion valve toward the second heat exchanger without passing through the liquid receiver in the defrosting mode.
The outdoor unit according to claim 2, further comprising:
a second expansion valve provided in the bypass flow path; and

a check valve provided in the bypass flow path, the check valve being configured to restrict flowing of the refrigerant to a direction from the second expansion valve toward the second heat exchanger.
The outdoor unit according to claim 2, wherein
the first compressor, the second heat exchanger, the first expansion valve, and the first heat exchanger constitute a first refrigeration cycle device that uses the first refrigerant, and

the outdoor unit further comprises:
a third heat exchanger configured to perform, in the refrigeration mode, heat exchange between the first refrigerant which is discharged from the second heat exchanger and flows into the liquid receiver and a second refrigerant; and

a second refrigeration cycle device in which the second refrigerant circulates in order of a second compressor, a fourth heat exchanger, a third expansion valve, and the third heat exchanger.
The outdoor unit according to claim 4, further comprising a fifth heat exchanger configured to perform, in the defrosting mode, heat exchange between the first refrigerant which is discharged from the liquid receiver and the first refrigerant flowing through the refrigerant exhaust pipe.
The outdoor unit according to claim 4, further comprising:
a circulation flow path connecting an inlet of the first refrigerant of the third heat exchanger with the outlet of the first refrigerant of the liquid receiver, the circulation flow path being configured to circulate the first refrigerant between the third heat exchanger and the liquid receiver; and

a solenoid valve provided in the circulation flow path.
A refrigeration apparatus comprising:
the outdoor unit according to any one of claims 1 to 6; and

the indoor unit.