ES2961815T3 - Refrigeration cycle device - Google Patents

Abstract

This refrigeration cycle device (100) is provided with a compressor (1), a first heat exchanger (3a), a second heat exchanger (3b), a third heat exchanger (5), a first expansion valve ( 4a) and a first switching unit (7). The first switching unit (7) can switch a first flow path (F1) and a second flow path (F2) between open and closed. If the first flow path (F1) is open, then the refrigerant circulates in the first circulation direction of the compressor (1), the first heat exchanger (3a), a first port (P1), a second port (P2) , the second heat exchanger (3b), the first expansion valve (4a) and the third heat exchanger (5). If the second flow path (F2) is open, then the refrigerant circulates in the second circulation direction of the compressor (1), the first heat exchanger (3a), the first port (P1), a third port (P3) , the first expansion valve (4a) and the third heat exchanger (5). When the circulation direction of the refrigerant is changed from the first circulation direction to the second circulation direction, part of the refrigerant remains in the second heat exchanger (3b). (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Refrigeration cycle device

Technical field

The present disclosure relates to a refrigeration cycle apparatus that circulates refrigerant.

Previous technique

A conventional refrigeration cycle apparatus that circulates refrigerant is known. For example, Japanese Patent Laid-Open No. 2015-87065 (PTL 1) discloses an air conditioner in which a part of the refrigerant filled in a refrigerant circuit is stored in a plurality of receivers, and the remaining refrigerant circulates in the coolant circuit. According to the air conditioner, by storing the refrigerant in a plurality of receivers, it is possible to adjust the amount of circulating refrigerant to an optimal amount in response to the operating conditions, which makes it possible to efficiently carry out the air conditioning operation. air.

PTL 2 describes an air conditioning system including: a first and a second heat exchanger on the use side and a heat exchanger on the heat source side respectively connected in series; a compressor connected between the first heat exchanger on the use side and the heat exchanger on the heat source side; an expansion valve connected between the first use-side heat exchanger and the second use-side heat exchanger; a pressure control device connected between the second heat exchanger on the utilization side and the heat exchanger on the heat source side; and a bypass valve connected between the expansion valve and the heat exchanger on the heat source side. The bypass valve provides a variable amount of liquid refrigerant flowing from the expansion valve to the heat exchanger on the heat source side.

The pressure control device and the bypass valve cooperate with each other to maintain the temperature of the compressor below a predetermined maximum allowable temperature for the compressor.

PTL 3 discloses a refrigeration apparatus that cools a charger for charging a storage battery upon receiving a supply of energy from a power source including: a compressor that circulates a refrigerant; a heat exchanger and a heat exchanger that carry out heat exchange between the refrigerant and the outside air; an expansion valve that reduces the pressure of the refrigerant; a heat exchanger that exchanges heat between the refrigerant and the air conditioner; a cooling unit arranged in a path along which the refrigerant flows between the heat exchanger and the expansion valve to cool the charger using the refrigerant; a refrigerant passage through which refrigerant flows between the compressor and the heat exchanger; a refrigerant passage through which refrigerant flows between the refrigeration unit and the expansion valve; and a connecting passage connecting the refrigerant passage and the refrigerant passage.

The PTL 4 document describes a triple supply air source heat pump system, including a first expansion valve, a first heat exchanger, a first water pump, a crossover valve, a compressor, a second water, a second heat exchanger, a second expansion valve and a third heat exchanger, one end of the first heat exchanger is connected to the third heat exchanger and the other end of the first heat exchanger is connected to the first heat exchanger , and the other end of the first heat exchanger is connected to the first water pump and the cross valve respectively, the third heat exchanger and one end of the second expansion valve is connected to the third heat exchanger, and the other end of the second expansion valve is connected to the cross valve, one end of the compressor is connected to the cross valve and the other end of the compressor is connected to the second heat exchanger, and the other end of the second heat exchanger is connected to the second water pump and to the cross valve respectively. This triple supply air source heat pump system of reasonable design and simple structure can realize automatic defrosting after forced air cooling in winter frost of heat exchanger, its convenient use has improved the availability factor.

Appointment list

Patent literature

PTL 1: Japanese Patent Open for Public Inspection No. 2015-87065

PTL 2: US 2014 /260386

PTL 3: WO 2012/143778 A1

PTL 4: CN 206247522 U

Summary of the invention

technical problem

According to the air conditioner disclosed in PTL 1, to adjust the amount of refrigerant circulating in the air conditioner (the amount of refrigerant circulating), it is necessary to have a plurality of receivers, which makes the air conditioner air is larger.

The present invention has been made to solve the problems described above, and an object of the present invention is to improve the operating efficiency of a refrigeration cycle apparatus while preventing the refrigeration cycle apparatus from increasing in size.

Solution to the problem

The present invention is defined by the attached claims. The refrigeration cycle apparatus according to the present invention circulates refrigerant. The refrigeration cycle apparatus includes, among others, a compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a first expansion valve, and a first switch. The first switch includes a first port, a second port, and a third port. The first switch switches each of a first flow path and a second flow path between an open state and a closed state. The first flow path connects the first port and the second port. The second flow path connects the first port and the third port. When the first flow path is open, the refrigerant flows in the first flow direction through the compressor, the first heat exchanger, the first port, the second port, the second heat exchanger, the first expansion valve and the third heat exchanger. When the second flow path is open, the refrigerant circulates in the second flow direction through the compressor, the first heat exchanger, the first port, the third port, the first expansion valve and the third heat exchanger. When the circulation direction of the refrigerant is switched from the first circulation direction to the second circulation direction, a part of the refrigerant is stored in the second heat exchanger.

Advantageous effects of the invention

According to the refrigeration cycle apparatus according to the present invention, when the circulation direction of the refrigerant is switched from the first circulation direction to the second circulation direction, a part of the refrigerant is stored in the second heat exchanger and, therefore, it is possible to improve the operating efficiency of the refrigeration cycle apparatus while preventing the refrigeration cycle apparatus from increasing in size.

Brief description of the drawings

Fig. 1 is a functional block diagram illustrating a configuration of an air conditioner serving as an example of a refrigeration cycle apparatus according to a first embodiment; Fig. 2 is a functional block diagram illustrating a configuration of a controller of Fig. 1; Fig. 3 is a diagram schematically illustrating a relationship between an amount of circulating refrigerant and the performance of the air conditioner of Fig. 1 during high load operation and low load operation;

Fig. 4 is a functional block diagram illustrating a configuration of an air conditioner serving as an example of the refrigeration cycle apparatus according to the first embodiment and a refrigerant flow during low load operation;

Fig. 5 is a flow chart illustrating a process to be performed by the controller of Fig. 1 on a switch during low load operation;

Fig. 6 is a diagram illustrating another coolant flow from a heat exchanger;

Fig. 7 is a functional block diagram illustrating a configuration of an air conditioner serving as an example of a refrigeration cycle apparatus according to a second embodiment and a flow of refrigerant during a load cooling operation high and a high load defrost operation;

Fig. 8 is a functional block diagram illustrating a configuration of an air conditioner serving as an example of a refrigeration cycle apparatus according to the second embodiment and a flow of refrigerant during a load cooling operation low and a low load defrost operation;

Fig. 9 is a functional block diagram illustrating a configuration of an air conditioner serving as an example of a refrigeration cycle apparatus according to the second embodiment and a flow of refrigerant during a charge heating operation high;

Fig. 10 is a functional block diagram illustrating a configuration of an air conditioner serving as an example of a refrigeration cycle apparatus according to the second embodiment and a flow of refrigerant during a charge heating operation low;

Fig. 11 is a flow chart illustrating a process to be performed by the controller of Fig. 9 on a switch during low load operation;

Fig. 12 is a flow chart illustrating an exemplary defrosting determination process to be performed by the controller during the heating operation;

Fig. 13 is a flow chart illustrating a process to be performed by the controller of Fig. 7 during a reverse defrost operation;

Fig. 14 is a diagram illustrating a flow of refrigerant when a condition for terminating a defrost operation in one heat exchanger is met but a condition for terminating a defrost operation in the other heat exchanger is not met;

Fig. 15 is a flow chart illustrating another exemplary defrosting determination process to be performed by the controller during the heating operation;

Fig. 16 is a functional block diagram illustrating a configuration of an air conditioner serving as an example of a refrigeration cycle apparatus according to a third embodiment;

Fig. 17 is a flow chart illustrating a process to be performed by the controller of Fig. 16 on a three-way valve during a low load cooling operation;

Fig. 18 is a flow chart illustrating a process to be performed by the controller of Fig. 16 on a three-way valve during a low load heating operation;

Fig. 19 is a flow chart illustrating an exemplary defrosting determination process to be performed by the controller during the heating operation; and

Fig. 20 is a flow chart illustrating another exemplary defrosting determination process to be performed by the controller during the heating operation.

Description of embodiments

Embodiments of the present invention will now be described herein in detail with reference to the drawings. It should be noted that in the drawings, the same or corresponding parts are indicated with the same reference numbers and the description thereof will not be repeated.

First embodiment

Fig. 1 is a functional block diagram illustrating a configuration of an air conditioner 100 serving as an example of a refrigeration cycle apparatus according to a first embodiment, which does not show all the characteristic features of the claim 1 but it will help to understand the invention as defined in claim 1. In Fig. 1, the main coolant flow is indicated by a thick line. The same applies to Fig. 4, 7 to 10 and 14 which will be described later.

As illustrated in Fig. 1, the air conditioner 100 includes an outdoor unit 110 and an indoor unit 120. The air conditioner 100 performs a cooling operation in an indoor space where the indoor unit 120 is installed. The outdoor unit 110 includes a compressor 1, a heat exchanger 3a (a first heat exchanger), a heat exchanger 3b (a second heat exchanger), an expansion valve 4a (a first expansion valve), a switch 7 (a first switch), a controller 50, temperature sensors 11, 12, 13 and 14, and an outdoor fan (not shown). The indoor unit 120 includes a heat exchanger 5 (a third heat exchanger) and an indoor fan (not shown). The controller 50 may be included in the indoor unit 120, or may be provided separately from the outdoor unit 110 and the indoor unit 120. In Fig. 1, the arrow G1 indicates the direction of gravity around the heat exchanger 3b. The same applies to Figs. 6 to 10, 14 and 16 which will be described later.

Switch 7 includes a port P1 (a first port), a port P2 (a second port), and a port P3 (a third port). Switch 7 selectively establishes a flow path F1 (a first flow path) and a flow path F2 (a second flow path). Flow path F1 communicates ports P1 and P2. Flow path F2 communicates ports P1 and P3.

When the flow path F1 is established, the refrigerant circulates in a circulation direction (a first circulation direction) through the compressor 1, the heat exchanger 3a, the port P1, the port P2, the heat exchanger 3b, the expansion valve 4a, and the heat exchanger 5. When the flow path F1 is established, both the heat exchanger 3a and the heat exchanger 3b function as a condenser, and the heat exchanger 5 functions as an evaporator. The refrigerant flows into the heat exchanger 3b from a port P4 (a fourth port) and leaves the heat exchanger 3b from a port P5 (a fifth port).

Each of the heat exchangers 3a, 3b and 5 is provided with a fan. The fan blows air to the corresponding heat exchanger to increase the efficiency of heat exchange between the refrigerant in the heat exchanger and the air. The fan may be, for example, a linear flow fan, a propeller fan, a turbofan or a multi-bladed fan. A plurality of fans may be provided for each heat exchanger, or a single fan may be provided for a plurality of heat exchangers.

The controller 50 obtains, from the temperature sensor 11 which is installed in a middle part of the heat exchanger 3a, a temperature T11 of the refrigerant flowing in the heat exchanger 3a. The controller 50 obtains, from the temperature sensor 12, a temperature T12 of the coolant flowing between the heat exchanger 3a and the switch 7. The controller 50 obtains, from the temperature sensor 13, a temperature T13 of the coolant flows between heat exchanger 3b and expansion valve 4a. The controller 50 obtains, from the temperature sensor 14, a temperature T14 of the indoor space where the indoor unit 120 is installed.

The controller 50 controls the amount of refrigerant discharged from the compressor 1 per unit of time by controlling the driving frequency of the compressor 1 according to a command value fc to bring the temperature T14 of the interior space to a target temperature (which can be set by a user, for example). The controller 50 uses the temperatures T 11 to T13 to calculate the degree of supercooling of the refrigerant leaving each heat exchanger that functions as a condenser.

The controller 50 controls the opening degree of the expansion valve 4a to maintain a pressure difference between a pressure of the refrigerant (high pressure side refrigerant) that is discharged from the compressor 1 without being depressurized and a pressure of the refrigerant (high pressure side refrigerant) low pressure side) that has been depressurized before being drawn into the compressor 1 within a desired range.

Fig. 2 is a functional block diagram illustrating the configuration of the controller 50 of Fig. 1. As illustrated in Fig. 2, the controller 50 includes a circuit 51, a memory 52 and an input/output unit 53. Circuit 51 may be dedicated hardware or may be a CPU (Central Processing Unit) that executes programs stored in memory 52. When circuit 51 is dedicated hardware, circuit 51 may be, for example, a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an ASIC (application specific integrated circuit), an FGA (field programmable gate array), or a combination thereof. When the circuit 51 is a CPU, the function of the controller 50 may be performed by software, firmware, or a combination of software and firmware. The software or firmware may be described as a program and stored in memory 52. Circuit 51 reads a program stored in memory and executes the program. The memory 52 includes a non-volatile or volatile semiconductor memory (for example, a RAM (random access memory), a ROM (read only memory), a flash memory, an EPROM (erasable programmable read only memory) or a EEPROM (electrically erasable programmable read-only memory), a magnetic disk, a floppy disk, an optical disk, a compact disk, an MD, or a DVD (Digital Versatile Disk). It should be noted that the CPU can be a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor or a DSP (digital signal processor).

The operating state of the air conditioner 100 is classified into high load operation and low load operation according to the load of compressor 1. The driving frequency of compressor 1 during high load operation is higher than the operating frequency of compressor 1. compressor 1 drive during low load operation. The operating state of the air conditioner 100 is determined from the command value fc sent to the compressor 1. For example, if the drive frequency of the compressor 1 represented by the command value fc is equal to or greater than a reference frequency, the operating state of the air conditioner 100 is determined as high load operation; and if the drive frequency is lower than the reference frequency, the operating state of the air conditioner 100 is determined as low load operation.

The command value fc can be changed in response to temperatures T11 to T14. For example, several gradual temperature ranges can be set in advance (e.g., 0°C or more and less than 1°C, 1°C or more and less than 2°C, and 2°C or more and less than 3 °C), and the drive frequency of the compressor 1 can be changed in response to any of the temperature ranges including therein the temperature difference between the temperature T14 and the target interior space temperature.

Fig. 3 is a diagram schematically illustrating a relationship between an amount of circulating refrigerant and the performance of the air conditioner 100 of Fig. 1 during high load operation and low load operation. For example, COP (Coefficient of Performance) is used as an index to indicate the performance of air conditioner 100. In Fig. 3, a curve C1 represents the relationship between an amount of circulating refrigerant and the performance of air conditioner 100. during high load operation. A curve C2 represents the relationship between an amount of circulating refrigerant and the performance of the air conditioner 100 during low load operation. M10 represents the total amount of refrigerant sealed in the air conditioner 100. Since a part of the total amount of refrigerant M10 can be dissolved in the refrigerator oil stored in the compressor 1, the amount of circulating refrigerant is less than the amount total coolant M10.

As illustrated in Fig. 3, during high load operation, the performance of the air conditioner 100 is maximum when the amount of circulating refrigerant is equal to M1. Thus, the total amount of refrigerant M10 in the air conditioner 100 is determined in such a way that the amount of circulating refrigerant obtained by subtracting the amount of refrigerant dissolved in the refrigerator oil or the like from the total amount of refrigerant M10 is equal to M1. On the other hand, during low load operation, the performance of the air conditioner 100 is maximum when the amount of circulating refrigerant is equal to M2 (M2<M1). Therefore, if the low load operation is performed when the circulating refrigerant amount is kept at M1, the performance of the air conditioner 100 is not maximum.

Therefore, the air conditioner 100 is started to perform low load operation from the state illustrated by a thick line in Fig. 1, when it is determined that the amount of circulating refrigerant is excessive, the flow path F2 It is established as illustrated by a thick line in Fig. 4 to separate the heat exchanger 3b from the coolant circulation path. Since the degree of supercooling of the refrigerant leaving a heat exchanger functioning as a condenser increases as the amount of refrigerant in circulation increases, whether the amount of refrigerant in circulation is excessive or not is determined by the degree of supercooling.

Once flow path F2 is established, the refrigerant circulates in one flow direction (a second flow direction) through compressor 1, heat exchanger 3a, port P1, port P3, expansion valve 4a and the heat exchanger 5. When the circulation direction of the refrigerant is switched from the circulation direction of Fig. 1 to the circulation direction of Fig. 4, a part of the refrigerant is stored in the heat exchanger 3b.

When the amount of circulating refrigerant is determined to be excessive during low load operation, the amount of refrigerant stored in the heat exchanger 3b is excluded from the circulating refrigerant amount M1, thereby improving the performance of the conditioner. 100 air pressure during low load operation. In the air conditioner 100, the heat exchanger 3b is designed in such a way that the amount of refrigerant obtained by subtracting the amount of refrigerant stored in the heat exchanger 3b from the amount of circulating refrigerant M1 is equal to M2. Since the heat exchanger 3b in the air conditioner 100 can be used as a container for adjusting the amount of circulating refrigerant, there is no need to provide another refrigerant container (such as a receiver) in addition to the heat exchanger 3b. According to the air conditioner 100, it is possible to improve the operating efficiency of the air conditioner 100 while preventing the air conditioner 100 from increasing in size.

Referring to Fig. 4, a flow path F3 extending from the heat exchanger 3b to the expansion valve 4a is connected to a flow path F4 (a fourth flow path) extending from port P3 in a connection portion N1 (a specific portion). To prevent the refrigerant from leaking out of the heat exchanger 3b, the connection portion N1 is preferably located at a higher position than the port P5. The height of the connection portion N1 may be the same as the height of the port P5.

In Fig. 4, although the heat exchanger 3b is separated from the flow path of the circulating refrigerant, since the port P5 is in communication with the flow path, the refrigerant is not sealed in the heat exchanger 3b. Even if the temperature of the heat exchanger 3b increases, the pressure of the refrigerant in the heat exchanger 3b hardly increases, which makes it possible to ensure the safety of the air conditioner 100.

Fig. 5 is a flow chart illustrating a process to be performed by the controller 50 of Fig. 1 on the switch 7 during low load operation. The process illustrated in Fig. 5 is called at regular intervals by a main routine (not shown) to perform comprehensive control on the air conditioner 100. Hereinafter, each stage may be simply referred to as "S".

As illustrated in Fig. 5, the controller 50 determines whether or not the flow path F1 is set to S101. If it is determined that the flow path F1 has been established (YES at S101), the controller 50 sets the degree of supercooling of the refrigerant leaving the heat exchanger 3b to "SC" at S102, and continues the process to S104. If it is determined that the flow path F1 is not established (NO at S101), the controller 50 sets the supercooling degree of the refrigerant leaving the heat exchanger 3a to "SC" at S103, and continues the process to S104.

At S104, the controller 50 determines whether the supercooling degree SC is greater than a reference value SC1. If it is determined that the degree of supercooling SC is greater than the reference value SC1 (YES at S104), the controller 50 continues the process to S107. If it is determined that the degree of supercooling SC is equal to or less than the reference value SC1 (NO in S104), the controller 50 determines whether or not the degree of supercooling SC is less than a reference value SC2 (SC2<SC1) in S105. If the supercooling degree SC is determined to be equal to or greater than the reference value SC2 (NOT in S105), the controller 50 returns the process to the main routine. If the supercooling degree SC is determined to be less than the reference value SC2 (YES at S105), the controller 50 sets the flow path F1 at S106 and continues the process to S107. Controller 50 sets flow path F2 to S107 and returns the process to the main routine.

The reference value SC1 and the reference value SC2 can be appropriately calculated by actual experiments or simulations. For example, the reference value SC1 and the reference value SC2 can be set as an upper limit (for example, 5°C) and a lower limit (for example, 3°C) of an allowed range (for example, 3 °C or more and 5°C or less) of the design values of the SC supercooling degree, respectively.

As described above, in the air conditioner 100, it is described that the connection portion N1 between the flow paths F3 and F4 is set at a higher position than the port P5. However, as illustrated in Fig. 6, if the flow path F3 has a portion N2 (specific portion) located at a higher position than the port P5, a connecting portion N1A between the flow paths F3 and F4 It may be located lower than port P5. The height of portion N2 may be the same as the height of port P5.

The sealed refrigerant in the air conditioner 100 includes, for example, an HFC (hydrofluorocarbon) refrigerant, an HFO (hydrofluoroolefin) refrigerant, an HC (hydrocarbon) refrigerant, or a non-azeotropic mixture type refrigerant (such as R454A). To reduce the GWP (Global Warming Point), an HC refrigerant (such as R290) or a non-azeotropic blend type refrigerant (such as R454A) can be used.

As described above, according to the refrigeration cycle apparatus according to the first embodiment, it is possible to improve the operating efficiency of the refrigeration cycle apparatus while preventing the refrigeration cycle apparatus from increasing in size.

Second embodiment

In the first embodiment, the description has been carried out on a refrigeration cycle apparatus that performs a cooling operation in the interior space where the indoor unit is arranged. In the second embodiment, a refrigeration cycle apparatus will be described that performs a heating operation and a cooling operation in the interior space and performs a defrosting operation during the heating operation.

Fig. 7 and 8 are functional block diagrams illustrating the configuration of an air conditioner 200 serving as an example of a refrigeration cycle apparatus according to the second embodiment and a flow of refrigerant during a cooling operation and a defrosting operation. The air conditioner 200 is different from the air conditioner 100 illustrated in Fig. 1 in that the air conditioner 200 further includes a four-way valve 2 (a second switch), an expansion valve 4b (a second valve expansion), temperature sensors 15 and 16, and a controller 50B instead of controller 50. The other components are the same and the description of them will not be repeated. In Fig. 7, the expansion valve 4b which is fully open is indicated by a dotted line. The same applies to Fig. 9 which will be described later.

As illustrated in Fig. 7, the expansion valve 4b is connected between the heat exchanger 3a and port P1. When the flow path F1 is established, the controller 50B fully opens the expansion valve 4b so that both the heat exchanger 3a and the heat exchanger 3b function as a condenser. As illustrated in Fig. 8, when the flow path F2 is established, the controller 50B controls the expansion valves 4a and 4b by adjusting the opening degrees of the expansion valves 4a and 4b to maintain the pressure difference between the high pressure side refrigerant and low pressure side refrigerant within a desired range. When the flow path F2 is established, the expansion valve 4a or the expansion valve 4b can be fully opened. The controller 50B controls the four-way valve 2 to switch the direction of refrigerant circulation. During a low load cooling operation and a low load defrosting operation in the air conditioner 200, the process illustrated in Fig. 5 is performed.

Fig. 9 and 10 are functional block diagrams illustrating a configuration of an air conditioner 200 serving as an example of a refrigeration cycle apparatus according to the second embodiment and a flow of refrigerant during a heating operation . As illustrated in Fig. 9, when the flow path F1 is established, the refrigerant circulates in a flow direction (a third flow direction) opposite to the flow direction illustrated in Fig. 7. When the flow path F1, both heat exchanger 3a and heat exchanger 3b function as an evaporator. When flow path F1 is established, controller 50B fully opens expansion valve 4b.

As illustrated in Fig. 10, when the flow path F2 is established, the refrigerant circulates in a flow direction (a fourth flow direction) opposite to the flow direction as illustrated in Fig. 8. When establishes flow path F2, heat exchanger 3a functions as an evaporator. When the flow path F2 is established, the controller 50B controls the expansion valves 4a and 4b by controlling the opening degrees of the expansion valves 4a and 4b to maintain the pressure difference between the high-pressure side refrigerant and the refrigerant. on the low pressure side within a desired range. When the flow path F2 is established, the expansion valve 4a or the expansion valve 4b can be fully opened. During the heating operation, the controller 50B uses the temperatures T15 and T16 to calculate the degree of supercooling of the refrigerant leaving the heat exchanger 5.

Fig. 11 is a flow chart illustrating a process to be performed by the controller 50B of Fig. 9 on the switch 7 during low load operation. The process illustrated in Fig. 11 is called at regular intervals by a main routine (not shown) to perform comprehensive control on the air conditioner 200. The same applies to the processes illustrated in Figs. 12 and 13 which are will describe later.

As illustrated in Fig. 11, the controller 50B determines whether or not the degree of supercooling SC is greater than a reference value SC3 at S201. If it is determined that the degree of supercooling SC is greater than the reference value SC3 (YES in S201), the controller 50B continues the process to S204. If it is determined that the degree of supercooling SC is equal to or less than the reference value SC3 (NO in S201), the controller 50B determines whether or not the degree of supercooling SC is less than a reference value SC4 (SC4<SC3) in S202. If the degree of supercooling SC is determined to be equal to or greater than the reference value SC4 (NOT in S202), the controller 50B returns the process to the main routine. If the degree of supercooling SC is determined to be less than the reference value SC4 (YES at S202), the controller 50B sets the flow path F1 at S203 and continues the process to S204. Controller 50B sets flow path F2 to S204 and returns the process to the main routine.

The reference value SC3 and the reference value SC4 are appropriately calculated by actual experiments or simulations. For example, the reference value SC3 and the reference value SC4 can be set as an upper limit (for example, 3°C) and a lower limit (for example, 1°C) of an allowed range (for example, 1 °C or more and 3°C or less) of the design values of the degree of supercooling<S c ,>respectively.

Fig. 12 is a flow chart illustrating an exemplary defrosting determination process to be performed by the controller 50B during the heating operation. As illustrated in Fig. 12, the controller 50B determines whether or not a condition is met to start a defrost operation in the heat exchanger 3b at S211. As an example of the condition for starting a defrosting operation in the heat exchanger 3b, a condition can be given in which the temperature T13 is lower than a reference temperature Ds1 (for example, -3°C). If it is determined that the condition for starting a defrost operation in the heat exchanger 3b is not met (NOT in S211), the controller 50B returns the process to the main routine.

If it is determined that the condition for starting a defrosting operation in the heat exchanger 3b is met (YES in S211), the controller 50B determines whether or not a condition for starting a defrosting operation in the heat exchanger 3a in S212. As an example of the condition for starting a defrost operation in the heat exchanger 3a, a condition can be given in which the temperature T11 is lower than a reference temperature Ds2 (for example, -3°C). If it is determined that the condition for starting a defrost operation in heat exchanger 3a is not met (NOT in S212), the controller 50B returns the process to the main routine. If it is determined that the condition for starting a defrost operation in the heat exchanger 3a is met (YES at S212), the controller 50B continues the process to S213.

At S213, the controller 50B establishes the flow path F1 and continues the process to S214. Controller 50B fully opens expansion valve 4b at S214 and continues the process to S215. At S215, the controller 50B changes the coolant circulation direction to the circulation direction as illustrated in Fig. 7 and returns the process to the main routine.

After S215, a reverse defrost operation is started. In reverse defrost operation, both heat exchanger 3a and heat exchanger 3b operate as a condenser. Heat exchangers 3a and 3b are defrosted by the condensation heat released by the refrigerant.

Fig. 13 is a flow chart illustrating a process to be performed by the controller 50B of Fig. 7 during the reverse defrost operation. As illustrated in Fig. 13, the controller 50B determines whether or not a condition for terminating a defrosting operation in the heat exchanger 3a at S221 is met. As an example of the condition for terminating a defrosting operation in the heat exchanger 3a, a condition may be given in which the temperature T11 is greater than a reference temperature Df1 (for example, 0°C). If it is determined that the condition for terminating a defrost operation in the heat exchanger 3a (NOT in S221) is not met, the controller 50B returns the process to the main routine. If it is determined that the condition for terminating a defrosting operation in the heat exchanger 3a is met (YES at S221), the controller 50B switches the refrigerant circulation direction at S222 and continues the process to S223.

At S223, the controller 50B determines whether or not a condition for terminating a defrosting operation in the heat exchanger 3b is met. As an example of the condition for terminating a defrosting operation in the heat exchanger 3b, a condition may be given in which the temperature T13 is greater than a reference temperature Df2 (for example, 0°C). If the condition for terminating a defrost operation in the heat exchanger 3b is determined to be met (YES at S223), the controller 50B fully opens the expansion valve 4b at S224 and returns the process to the main routine. The controller 50B controls the opening degree of the expansion valve 4a to maintain the pressure difference between the high pressure side refrigerant and the low pressure side refrigerant within a desired range. If it is determined that the condition for terminating a defrost operation in the heat exchanger 3b (NO at S223) is not met, the controller 50B fully opens the expansion valve 4a at S225 and returns the process to the main routine.

Fig. 14 is a diagram illustrating a refrigerant flow when the condition for terminating a defrosting operation in the heat exchanger 3a is met but the condition for terminating a defrosting operation in the heat exchanger 3b is not met (when S225 of Fig. 13 is performed). As illustrated in Fig. 14, since the expansion valve 4a is fully open, the heat exchanger 3b functions as a condenser. The heat exchanger 3b is defrosted by the condensation heat released by the refrigerant. Heating the heat exchanger 3b by the condensation heat released by the refrigerant is performed after the condition for completing a defrosting operation in the heat exchanger 3b is met. The controller 50B controls the opening degree of the expansion valve 4b to maintain the pressure difference between the high pressure side refrigerant and the low pressure side refrigerant within a desired range. Once the defrosting operation is completed in both heat exchanger 3a and heat exchanger 3b, the heating operation is restarted. The reset warm-up operation can be a high load operation or a low load operation.

Heating the heat exchanger 3b by condensation heat released from the refrigerant can be carried out to prevent frost from forming on the heat exchanger 3b. Fig. 15 is a flow chart illustrating another exemplary defrosting determination process to be performed by the controller 50B during the heating operation. The flow chart illustrated in Fig. 15 is different from the flow chart illustrated in Fig. 12 with the addition of S216 and a reverse order of S212 and S213.

As illustrated in Fig. 15, if it is determined that the condition for starting a defrost operation in the heat exchanger 3b is met (YES at S211), the controller 50B sets the flow path F1 at S213 and continues the process. to S212. If it is determined that the condition for starting a defrost operation in the heat exchanger 3a (NO at S212) is not met, the controller 50B fully opens the expansion valve 4a at S216 and returns the process to the main routine.

The refrigerant flow in the air conditioner 200 after S216 is the same as the refrigerant flow as illustrated in Fig. 14. In the air conditioner 200, since the expansion valve 4b is connected between the refrigerant exchangers heat 3b and 3a, the expansion valve 4a can be fully opened to allow liquid refrigerant to flow into the heat exchanger 3b. Since it is possible to store the liquid refrigerant in the heat exchanger 3b, compared to the case where the expansion valve 4b is not provided and the refrigerant in the two-phase gas-liquid state after depressurization by the expansion valve 4a is stored in the heat exchanger 3b, the heat exchanger 3b can be made smaller.

In the air conditioner 200, since the defrosting operation can be performed in the heat exchanger 3b without stopping the heating operation, it is possible to prevent the temperature of the interior space from decreasing by reverse defrosting operation. In addition, when the non-azeotropic mixture type refrigerant is sealed as a refrigerant, due to the temperature gradient, frost is likely to form around the port P5 of the heat exchanger 3b. In the air conditioner 200, since the refrigerant having a relatively high temperature flows into the heat exchanger 3b during the heating operation, it is possible to prevent frost from forming around the port P5 of the heat exchanger 3b. Furthermore, preventing frost in the heat exchanger 3b makes it possible to prevent frost from spreading to the heat exchanger 3a.

As described above, according to the refrigeration cycle apparatus of the second embodiment, it is possible to improve the operating efficiency of the refrigeration cycle apparatus during any of the cooling operation, the heating operation or the defrosting operation by avoiding at the same time as the refrigeration cycle apparatus increases in size.

Third embodiment

In the first embodiment and the second embodiment, it is described that the first switch can selectively establish the first flow path and the second flow path. In the third embodiment, the description will be carried out in the sense that the first switch can set both the first flow path and the second flow path in an open state.

Fig. 16 is a functional block diagram illustrating the configuration of an air conditioner 300 that serves as an example of a refrigeration cycle apparatus according to the third embodiment. The air conditioner 300 is different from the air conditioner 200 illustrated in Fig. 7 in that the switch 7 and the controller 50B in Fig. 7 are replaced by a three-way valve 7C and a controller 50C, respectively. The other components are the same and their description will not be repeated.

As illustrated in Fig. 16, the three-way valve 7C includes a port P31 (a first port), a port P32 (a second port), a port P33 (a third port), a flow path F31 (a first flow path), and a flow path F32 (a second flow path). Flow path F31 communicates ports P31 and P32. Flow path F32 connects ports P31 and P33. The three-way valve 7C can switch the flow paths F31 and F32 between an open state and a closed state.

Fig. 17 is a flow chart illustrating a process to be performed by the controller 50C of Fig. 16 on the three-way valve 7C during a low load cooling operation. The process illustrated in Fig. 17 is called at regular intervals by a main routine (not shown) to perform comprehensive control on the air conditioner 300. The same applies to the process illustrated in Fig. 18.

As illustrated in Fig. 17, the controller 50C determines whether the flow path F31 is open or not at S301. If the flow path F31 is determined to be open (YES at S301), the controller 50C sets the degree of supercooling of the refrigerant leaving the heat exchanger 3b to "SC" at S302, and continues the process to S304. If the flow path F31 is determined to be closed (NO at S301), the controller 50<c>sets the degree of supercooling of the refrigerant leaving the heat exchanger 3a to "SC" at S303, and continues the process to S304 .

At S304, the controller 50C determines whether or not the supercooling degree SC is greater than a reference value SC1. If it is determined that the degree of supercooling SC is greater than the reference value SC1 (YES in S304), the controller 50C continues the process to S307.

If the supercooling degree SC is determined to be equal to or less than a reference value SC1 (NO in S304), the controller 50C determines whether or not the supercooling degree SC is less than a reference value SC2 in S305. If the degree of supercooling SC is determined to be equal to or greater than the reference value SC2 (NOT in S305), the controller 50C returns the process to the main routine. If it is determined that the supercooling degree SC is less than the reference value SC2 (YES at S305), the controller 50C opens the flow path F31 at S306 and continues the process to S307.

In step S307, the controller 50C opens the flow path F32 and continues the process to step S308. At S308, the controller 50C closes the flow path F31 and returns the process to the main routine.

When S306 and S307 are performed in this order, since both flow paths F31 and F32 are open, it is possible to prevent the amount of refrigerant stored in the heat exchanger 3b from changing rapidly. As a result, it is possible to easily maintain the degree of supercooling SC within the allowable range of design values, and it is possible to prevent the performance of the air conditioner 200 (such as the temperature of the air blown from the indoor unit 120 to the indoor space) from varying. ).

Fig. 18 is a flow chart illustrating a process to be performed by the controller 50C of Fig. 16 on the three-way valve 7C during low load heating operation. The process illustrated in Fig. 11 is called at regular intervals by a main routine (not shown) to perform comprehensive control on the air conditioner 200. The same applies to the processes illustrated in Figs. 12 and 13 which are described later.

As illustrated in Fig. 18, the controller 50C determines whether the degree of supercooling SC is greater than a reference value SC3 at S311. If it is determined that the degree of supercooling SC is greater than the reference value SC3 (YES in S311), the controller 50C continues the process to S314. If it is determined that the degree of supercooling SC is equal to or less than the reference value SC3 (NOT in S311), the controller 50C determines whether or not the degree of supercooling SC is less than a reference value SC4 (SC4<SC3) in S312. If the degree of supercooling SC is determined to be equal to or greater than the reference value SC4 (NOT in S312), the controller 50C returns the process to the main routine. If the supercooling degree SC is determined to be less than the reference value SC4 (YES at S312), the controller 50C opens the flow path F31 at S313 and continues the process to S314.

In step S314, controller 50C opens flow path F32 and continues the process to step S315. At S315, the controller 50C closes the flow path F31 and returns the process to the main routine.

Fig. 19 is a flow chart illustrating an exemplary defrosting determination process to be performed by the controller 50C during heating operation. The flow chart illustrated in Fig. 19 is different from the flow chart illustrated in Fig. 12 in that S213 in Fig. 12 is replaced by S323, and S324 is performed between S323 and S214.

As illustrated in Fig. 19, if it is determined that the condition for starting a defrosting operation in the heat exchanger 3b is met (YES in S211) and the condition for starting a defrosting operation in the heat exchanger is met 3a (YES at S212), controller 50C opens flow path F31 at S323, closes flow path F32 at S324, and continues the process to S214. The controller 50C performs S214 and S215 similarly to the second embodiment and returns the process to the main routine.

Fig. 20 is a flow chart illustrating another exemplary defrosting determination process to be performed by the controller 50C during the heating operation. The flow chart illustrated in Fig. 20 is obtained in such a way that S213 of Fig. 15 is replaced by S323 of Fig. 19, and S324 of Fig. 19 is realized between S323 and S212 in Fig. 20 During the reverse defrost operation, the controller 50C performs the process illustrated in Fig. 14.

As illustrated in Fig. 20, if it is determined that the condition for starting a defrost operation in the heat exchanger 3b<(Yes>in S211) is met, the controller<5 0 c>opens the flow path F31 at S323, closes flow path F32 at S324 and continues the process to S212. The controller 50C performs S212 and S214 to S216 similarly to the second embodiment, and returns the process to the main routine.

Instead of the three-way valve 7C, an electronic expansion valve can be connected to each of the flow paths F31 and F32. It is desirable that the amount of refrigerant flowing through each of the flow paths F31 and F32 per unit of time be adjustable.

As described above, according to the refrigeration cycle apparatus of the third embodiment, it is possible to improve the operating efficiency of a refrigeration cycle apparatus while preventing the refrigeration cycle apparatus from increasing in size.

The embodiments disclosed herein are intended to be appropriately combined as long as they are not technically inconsistent with each other. It should be understood that the embodiment disclosed herein is merely by way of illustration and example, but is not limited in all respects. The scope of the present invention is defined by the terms of the claims, rather than the preceding description, and is intended to include any modifications within the meaning of the terms of the claims.

List of reference signs

1: compressor; 2: four-way valve; 3a, 3b, 5: heat exchanger; 4a, 4b: expansion valve; 7: switch; 7C: three-way valve; 11 to 16: temperature sensor; 50, 50B, 50C: controller; 51: processing circuit; 52: memory; 53: input/output unit; 100, 200, 300; air-conditioning; 110: outdoor unit; 120: indoor unit; F1 to F4, F31, F32: flow path; P1 to P5, P31 to P33: port

Claims (8)

1. A refrigeration cycle apparatus (200, 300) that circulates refrigerant, the refrigeration cycle apparatus (200, 300) comprising: a compressor (1); a first heat exchanger (3a); a second heat exchanger (3b); a third heat exchanger (5); a first expansion valve (4a); a first switch (7) that includes a first port (P1), a second port (P2) and a third port (P3), a controller (50B, 50C) that is configured to control the first switch (7); and a second expansion valve (4b) which is connected between the first heat exchanger (3a) and the second heat exchanger (3b), the first switch (7) switching each of a first flow path (F1, F31) and a second flow path (F2, F32) between an open state and a closed state, communicating the first flow path (F1, F31 ) the first port (P1) and the second port (P2), and the second flow path (F2, F32) communicating the first port (P1) and the third port (P3), when the first flow path (F1, F31) is open, circulating the refrigerant in a first direction of circulation through the compressor (1), the first heat exchanger (3a), the first port (P1), the second port (P2), the second heat exchanger (3b), the first expansion valve (4a), and the third heat exchanger (5), when the second flow path (F2, F32) is open, circulating the refrigerant in a second direction of circulation through the compressor (1), the first heat exchanger (3a), the first port (P1), the third port (P3), the first expansion valve (4a), and the third heat exchanger (5), and when the circulation direction of the refrigerant is switched from the first circulation direction to the second circulation direction, a part of the refrigerant is stored in the second heat exchanger (3b), wherein the controller (50B, 50C) is configured to open the first flow path (F1, F31) when the degree of supercooling of the refrigerant flowing to the first expansion valve (4a) is less than a reference value ( SC1), wherein the refrigeration cycle apparatus (200, 300) further includes a second switch (2) that is configured to switch the direction of circulation of the refrigerant between the first direction of circulation and a third direction of circulation opposite to the first flow direction, and to switch the flow direction of the refrigerant between the second flow direction and a fourth flow direction opposite to the second flow direction, when the circulation direction of the refrigerant is the first circulation direction or the second circulation direction, and when a condition for ending a defrosting operation in the first heat exchanger (3a) is met and a condition for ending a defrosting operation is not met. defrosting operation in the second heat exchanger (3b), the controller (50B, 50C) is configured to open the first flow path (F1, F31) to switch the circulation direction of the refrigerant to the third circulation direction, and completely open the first expansion valve (4a). 2. The refrigeration cycle apparatus (200) according to claim 1, wherein The first switch (7) is configured to selectively establish the first flow path (F1) and the second flow path (F2). 3. The refrigeration cycle apparatus (200, 300) according to claim 1 or 2, wherein The second heat exchanger (3b) includes: a fourth port (P4) through which the refrigerant flows to the second heat exchanger (3b) in the first flow direction; and a fifth port (P5) through which the refrigerant leaves the second heat exchanger (3b) in the first direction of circulation, a third flow path (F3) that extends from the second heat exchanger (3b) to The first expansion valve (4a) includes a specific portion (N1) located in a position higher than the fifth port (P5). 4. The refrigeration cycle apparatus (200, 300) according to claim 3, wherein a fourth flow path (F4) extending from the third port (P3) to the third flow path (F3) is connected to the third flow path (F3) in the specific portion (N1). 5. The refrigeration cycle apparatus (200, 300) according to claim 1, wherein The controller (50B, 50C) is configured to open the second flow path (F2, F32) when the degree of supercooling is greater than the reference value (SC1). 6. The refrigeration cycle apparatus (200, 300) according to any one of claims 1 to 5, wherein when the circulation direction of the refrigerant is the third circulation direction or the fourth circulation direction, and when a condition for starting a defrosting operation in the second heat exchanger (3b) is met and a condition for starting a defrosting operation is not met. defrosting operation in the first heat exchanger (3a), the controller (50B, 50C) is configured to open the first flow path (F1, F31) and to fully open the first expansion valve (4a). 7. The refrigeration cycle apparatus (200, 300) according to any of claims 1 to 6, wherein The coolant includes HC (hydrocarbon) coolant. 8. The refrigeration cycle apparatus (200, 300) according to any of claims 1 to 7, wherein The coolant includes a non-azeotropic mixture type coolant.