Refrigeration device

Abstract

The present disclosure provides a refrigeration device capable of providing optimal heating conditions during heating operation and performing stable heating operation. A refrigeration device in the present disclosure includes: an outdoor unit 10 including a compressor 11 and an outdoor heat exchanger 13; a plurality of indoor units 20 positioned in parallel with the outdoor unit 10, the indoor units 20 each including an indoor heat exchanger 21, an indoor blower 22, and an indoor expansion valve 25; and a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle. Each of the indoor units 20 can set an indoor temperature. The refrigeration device includes a control unit 40, the control unit 40 setting a control target value for each indoor unit 20 so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger 21 to be a set temperature during heating operation, the control unit 40 adjusting an opening degree of the indoor expansion valve 25 based on the control target value so as to cause the average value to approach the set temperature of each indoor unit 20.

Description

Technical Field

[0001] The present disclosure relates to a refrigeration device.Background Art

[0002] Patent Literature 1 discloses an air-conditioning device having control means for executing refrigerant amount balance control that adjusts an opening degree of each indoor expansion valve when the air-conditioning device performs heating operation, so as to cause the degree of refrigerant subcooling of each indoor unit to be the average degree of refrigerant subcooling calculated using the maximum value and minimum value of the degree of refrigerant subcooling, or so as to cause the heat exchanger outlet temperature of each indoor unit to be the average heat exchanger outlet temperature calculated using the maximum value and minimum value of the heat exchanger outlet temperature.Citation ListPatent Literature

[0003] Patent Literature 1: Japanese Patent Laid-Open No. 2017-122557Summary of InventionTechnical Problem

[0004] The present disclosure provides a refrigeration device capable of providing optimal heating conditions during heating operation and performing stable heating operation.Solution to Problem

[0005] The refrigeration device in the present disclosure is a refrigeration device including: an outdoor unit including a compressor and an outdoor heat exchanger; a plurality of indoor units positioned in parallel with the outdoor unit, the indoor units each including an indoor heat exchanger, an indoor blower, and an indoor expansion valve, the indoor heat exchanger performing heating operation as a radiator; a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle, wherein each of the indoor units can set an indoor temperature; and a control unit, the control unit setting a control target value for each indoor unit so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger to be a set temperature during heating operation, the control unit adjusting an opening degree of the indoor expansion valve based on the control target value so as to cause the average value to approach the set temperature of each indoor unit.

[0006] This description is intended to include the entire contents of Japanese Patent Application No. 2023-061107, filed on April 5, 2023.Advantageous Effects of Invention

[0007] In the refrigeration device in the present disclosure, the control unit sets the control target value for each indoor unit so as to cause the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger to be the set temperature, and adjusts the opening degree of the indoor expansion valve so as to cause the average value to approach the set temperature of each indoor unit based on the control target value. This makes it possible to provide optimal heating conditions even when refrigerant having a high pressure of a critical pressure or higher is sent to the indoor heat exchanger and the temperature gradient due to the heating load changes. This makes it possible to prevent insufficiently heated air from being blown out of the indoor heat exchanger and perform stable heating operation.Brief Description of the Drawings

[0008] [FIG. 1] FIG. 1 is a refrigeration cycle circuit diagram for an air-conditioning device in Embodiment 1. [FIG. 2] FIG. 2 is a block diagram showing a control configuration in Embodiment 1. [FIG. 3] FIG. 3 is a refrigeration cycle circuit diagram of an air-conditioning device in Embodiment 2. [FIG. 4] FIG. 4 is a block diagram showing a control configuration in Embodiment 2. [FIG. 5] FIG. 5 is a graph showing a relationship between refrigerant temperature and refrigerant flow path position in the indoor heat exchanger in Embodiment 2. Description of Embodiments(Knowledge etc. on which the present disclosure is based)

[0009] At the time when the inventors came up with the present disclosure, one of problems that occur during heating operation using HFC refrigerants was that the refrigerant, when it condenses, would not flow evenly to a plurality of indoor units due to differences in flow path resistances.

[0010] In contrast, when a refrigerant in a supercritical state, such as carbon dioxide refrigerant, is used, condensation does not occur, so that there is not this disadvantage. However, the refrigerant in the indoor heat exchanger undergoes sensible heat change, resulting in a large temperature gradient in the heat exchanger temperature from the inlet toward the outlet of refrigerant. This creates a large temperature difference in the heat exchanger, resulting in an disadvantage of inability to sufficiently heat the blown air. The inventors have discovered this problem and come to create the subject matter of the present disclosure in order to solve this problem.

[0011] The present disclosure therefore provides a refrigeration device capable of providing optimal heating conditions during heating operation and performing stable heating operation.

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed description may be omitted for already well-known matters, or duplicate description may be omitted for substantially the same configurations. This is to avoid the following description from being more redundant than necessary and to facilitate understanding of those skilled in the art.

[0013] Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.(Embodiment 1)

[0014] The following describes Embodiment 1.[1-1. Configuration][1-1-1. Configuration of refrigeration cycle circuit]

[0015] FIG. 1 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1.

[0016] The air-conditioning device 1 includes an outdoor unit 10 and a plurality of indoor units 20 (two in this embodiment). In this embodiment, the air-conditioning device 1 uses carbon dioxide refrigerant as a refrigerant.

[0017] The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor blower 14, and an outdoor expansion valve 15.

[0018] The compressor 11 is, for example, a scroll compressor, which sucks, compresses, and discharges the refrigerant. The four-way valve 12 is a device that communicates with the discharge side of the compressor 11, the suction side of the compressor 11, the outdoor heat exchanger 13, and the high-temperature side refrigerant piping, and is capable of switching the refrigerant flow path.

[0019] The outdoor heat exchanger 13 is, for example, a fin-tube heat exchanger having heat transfer tubes and plate fins, and exchanges heat between the refrigerant flowing inside and the outside air. The outdoor blower 14 is a so-called axial fan that has a fan 16 with multiple blades and a fan motor 17 that rotates the fan 16.

[0020] The four-way valve 12 switches the refrigerant flow path, thereby switching the operation of the air-conditioning device between heating operation, in which the refrigerant in the indoor heat exchanger radiates heat, and cooling operation, in which the refrigerant in the indoor heat exchanger absorbs heat.

[0021] Each indoor unit 20 is a device installed indoors to condition the air therein, and includes an indoor heat exchanger 21 and an indoor blower 22.

[0022] The indoor heat exchanger 21 is, for example, a so-called fin-tube heat exchanger including heat transfer tubes and plate fins.

[0023] The indoor blower 22 is a so-called axial fan including a fan 23 having multiple blades and a fan motor 24 that rotates the fan 23. Note that the indoor blower 22 may use any blower, such as a crossflow fan, sirocco fan, or blower.

[0024] The indoor units 20 are connected in parallel to the outdoor unit 10 via refrigerant piping 30 through which the refrigerant flows.

[0025] The refrigerant piping branches into two parts respectively toward the two indoor units 20, and each of the parts has an indoor expansion valve 25 installed thereon to adjust the refrigerant flow rate and reduce the pressure.

[0026] On the refrigerant inlet-side and the refrigerant outlet-side of each indoor heat exchanger 21 during heating operation, an inlet-side refrigerant temperature detection sensor 26 and an outlet-side refrigerant temperature detection sensor 27 are provided each detecting a corresponding refrigerant temperature.

[0027] Each indoor unit 20 is provided with an intake air temperature sensor 28 that detects the temperature of the intake air sent to the indoor heat exchanger 21. In addition, a room temperature sensor 42 (see FIG. 2) is provided indoors to detect the temperature of the indoor air.[1-1-2. Control configuration]

[0028] Next, a control configuration of the air-conditioning device 1 will be described.

[0029] FIG. 2 is a block diagram showing a control configuration of Embodiment 1.

[0030] As shown in FIG. 2, the air-conditioning device 1 includes a control unit 40. The control unit 40 may be provided in the outdoor unit 10 or may be provided in the indoor units 20.

[0031] The control unit 40 includes a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and a memory unit 41. The memory unit 41 of the control unit 40 has a volatile memory and a non-volatile memory unit. The volatile memory is, for example, RAM (Random Access Memory). The non-volatile memory unit is composed of ROM (Read Only Memory), a hard disk, flash memory, etc. The control unit 40 is also communicatively connected to the various devices of the air-conditioning device 1 via wired communication means such as signal lines, or wireless communication means such as wireless communication circuits.

[0032] The control unit 40 executes a program stored in the memory unit 41 to control the operation of various devices, such as the compressor 11, the four-way valve 12, the indoor expansion valves 25, the outdoor expansion valve 15, the outdoor blower 14, and the indoor blowers 22, based on the values detected by the inlet-side refrigerant temperature detection sensors 26, the outlet-side refrigerant temperature detection sensors 27, the intake air temperature sensors 28, and the room temperature sensor 42.[1-2. Operation]

[0033] Next, operation of the air-conditioning device 1 will be described.

[0034] First, when performing heating operation, the control unit 40 switches the four-way valve 12 in the direction indicated by the dashed line in FIG. 1 and drives the compressor 11.

[0035] Driving the compressor 11 causes the refrigerant to have a high pressure of a critical pressure or higher and to be discharged from the compressor 11. The refrigerant is then sent to each indoor heat exchanger 21 through the refrigerant piping and the four-way valve 12.

[0036] The refrigerant sent to the indoor heat exchanger 21 exchanges heat with the indoor air flowing through the indoor heat exchanger 21, with the indoor blower 22.

[0037] The indoor air is warmed through heat exchange with the refrigerant, and is sent indoors. After heat exchange, the refrigerant temperature drops to approximately the same temperature as the indoor air, and the refrigerant is sent to the outdoor unit 10 through the indoor expansion valve 25.

[0038] The refrigerant sent to the outdoor unit 10 is returned to the compressor 11 through the outdoor expansion mechanism, the outdoor heat exchanger 13, and the four-way valve 12.

[0039] During heating operation of each indoor heat exchanger 21, the control unit 40 controls the high pressure of the refrigerant to a supercritical pressure or higher. A value of the pressure is determined based on the difference between the blow temperature from the intake air temperature sensor 28 of the indoor heat exchanger 21 and a set temperature.

[0040] This allows the appropriate amount of refrigerant to be sent to the indoor heat exchanger 21, preventing refrigerant from stagnation in the indoor heat exchanger 21 and minimizing changes in the amount of refrigerant required throughout the year.

[0041] During heating operation, the control unit 40 acquires the inlet-side refrigerant temperature of each indoor heat exchanger 21 from the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature of the indoor heat exchanger 21 from the outlet-side refrigerant temperature detection sensor 27.

[0042] The control unit 40 calculates the average value of the inlet-side refrigerant temperature from the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature from the outlet-side refrigerant temperature detection sensor 27.

[0043] The control unit 40 sets a control target value for each indoor unit 20 so as to cause the average value of the calculated refrigerant temperatures to be the set temperature, and controls the indoor expansion valve 25 to adjust its opening degree so as to cause the average value to approach the set temperature of each indoor unit 20 based on the control target value.

[0044] In other words, when carbon dioxide refrigerant is used, the refrigerant discharged from the compressor 11 flows into the indoor heat exchangers 21 in a supercritical state. In the case of carbon dioxide refrigerant, heat exchange with the indoor air in each indoor heat exchanger 21 causes a sensible heat change, decreasing the refrigerant temperature to approach that of the indoor air.

[0045] At this time, the amount of refrigerant temperature drop varies depending on the amount of refrigerant flowing through the indoor heat exchanger 21 and the amount of airflow from the indoor blower 22.

[0046] In this embodiment, control is performed based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature so as to cause the average value to have an appropriate temperature difference from the set temperature. This allows the temperature of the indoor heat exchanger 21 to be appropriately controlled even when carbon dioxide refrigerant is used and the temperature gradient from the inlet-side toward the outlet-side of the indoor heat exchanger 21 changes.

[0047] When controlling based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature, the control unit 40 performs control with a control target value obtained by adding ΔT to the set temperature depending on the difference between the indoor air temperature and the set temperature.

[0048] In other words, when the difference between the indoor air temperature and the set temperature is large, control based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature is presumably insufficient. For this reason, control is performed based on the value of ΔT to be added to the set temperature.

[0049] ΔT is set in advance based on indicators such as the temperature difference between the indoor air temperature and the set temperature, the airflow rate made by the indoor blower 22, and the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature. For ΔT, values set in advance are stored in the memory unit 41 as a data table. The control unit 40 reads the required value from the data table in the memory unit 41 and performs control.

[0050] As a result, even when there is a large difference between the indoor temperature and the set temperature, it is possible to control the indoor temperature to approach the set temperature with the optimal amount of heating.

[0051] Furthermore, when the value of ΔT becomes equal to or smaller than a predetermined value, the indoor temperature has approached the set temperature and the amount of heat in the indoor heat exchanger 21 is excessive. Therefore, the control unit 40 first controls the compressor drive frequency to be reduced. Then, the control unit 40 controls the indoor expansion valve 25 to gradually close.

[0052] When the amount of closure of the expansion valve reaches its limit, the control unit 40 controls the airflow rate of the indoor blower 22 to be reduced until ΔT exceeds a specified value.

[0053] In this way, since the refrigerant in the indoor heat exchanger 21 presumably has an excessive amount of heat when the value of ΔT is equal to or smaller than a predetermined value, the compressor drive frequency is controlled to be reduced, the expansion valve is controlled to be closed, and the airflow rate of the indoor blower 22 is controlled to be reduced, making it possible to prevent the expansion valve from closing too much and control the amount of heat of the refrigerant in the indoor heat exchanger 21.

[0054] Furthermore, when the value of ΔT exceeds the specified value, the control unit 40 controls the expansion valve to be open.

[0055] In this way, the expansion valve opening degree is controlled based on whether the ΔT value is equal to or smaller than a predetermined value or greater than the predetermined value. In this case, if the airflow rate of the indoor blower 22 is high, the expansion valve is closed excessively. Therefore, the airflow rate of the indoor blower 22 is controlled in accordance with the opening degree of the expansion valve.

[0056] This allows the expansion valve to keep the opening degree at a predetermined degree or higher while maintaining an appropriate refrigerant heat amount in the indoor heat exchanger 21.[1-3. Effects, etc.]

[0057] As described above, in this embodiment, the refrigeration device includes: an outdoor unit 10 including a compressor 11 and an outdoor heat exchanger 13; a plurality of indoor units 20 positioned in parallel with the outdoor unit 10, the indoor units 20 each including an indoor heat exchanger 21, an indoor blower 22, and an indoor expansion valve 25; and a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle. Each of the indoor units 20 can set an indoor temperature. The refrigeration device includes a control unit 40, the control unit 40 setting a control target value for each indoor unit 20 so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger 21 to be a set temperature during heating operation, the control unit 40 adjusting an opening degree of the indoor expansion valve 25 based on the control target value so as to cause the average value to approach the set temperature of each indoor unit 20.

[0058] According to this configuration, the control unit 40 sets the control target value of each indoor unit 20 to cause the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger 21 to be the set temperature. The control unit 40 then adjusts the opening degree of the indoor expansion valve 25 based on the control target value so as to cause the average value to approach the set temperature of each indoor unit 20. This can provide optimal heating conditions even when refrigerant having a high pressure of a critical pressure or higher is sent to the indoor heat exchanger 21 and the temperature gradient changes due to the heating load. This makes it possible to prevent insufficiently heated air from being blown out of the indoor heat exchanger 21 and perform stable heating operation.

[0059] In this embodiment, the control unit 40 sets the control target value for each indoor unit to a value obtained by adding a predetermined value ΔT to the set temperature.

[0060] With this configuration, the value obtained by adding ΔT to the set temperature is set to the control target value. This allows the capacity made by the indoor heat exchanger 21 to be increased in accordance with the difference between the indoor temperature and the set temperature, and allows the indoor temperature to be controlled to approach the set temperature depending on the difference between the indoor temperature and the set temperature.

[0061] In this embodiment, when the value of ΔT to be added to the set temperature becomes equal to or smaller than a predetermined value, the control unit 40 controls the indoor blower 22 to reduce the airflow rate until the value of ΔT exceeds the specified value, and when the value of ΔT exceeds the specified value, the control unit 40 controls the indoor blower 22 to maintain or increase the airflow rate.

[0062] With this configuration, when the value of ΔT becomes equal to or lower than a predetermined value, the airflow rate of the indoor blower 22 is reduced, thereby making it possible to reduce the amount of heat exchanged by the indoor heat exchanger 21, maintain the temperature of the indoor heat exchanger 21, and create a state in which the value of ΔT is equal to or larger than a predetermined value. This can prevent the indoor expansion valve 25 from being closed excessively, securing a certain refrigerant flow rate or more. In addition, when the value of ΔT exceeds a predetermined value, the control unit 40 maintains or increases the airflow rate of the indoor blower 22, making it possible to secure the heat exchange amount in the indoor heat exchanger 21.

[0063] In this embodiment, during heating operation of each indoor heat exchanger 21, the control unit 40 controls the high pressure of the refrigerant to a supercritical pressure or higher. A value of the pressure is determined based on the difference between the blow temperature from the intake air temperature sensor 28 of the indoor heat exchanger 21 and the set temperature.

[0064] This configuration allows an appropriate amount of refrigerant to be sent to the indoor heat exchanger 21, preventing refrigerant stagnation in the indoor heat exchanger 21 and minimizing changes in the amount of refrigerant required throughout the year.(Embodiment 2)

[0065] The following describes Embodiment 2 of the present disclosure.[2-1. Configuration]

[0066] FIG. 3 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1 of Embodiment 2. FIG. 4 is a block diagram showing a control configuration of Embodiment 2.

[0067] As shown in FIGS. 3 and 4, in this embodiment, a refrigerant temperature sensor 43 is provided midway through the refrigerant flow path inside each indoor heat exchanger 21.

[0068] In this embodiment, the control unit 40 executes a program stored in the memory unit 41 to control the operation of various devices, such as the compressor 11, the four-way valve 12, the indoor expansion valves 25, the outdoor expansion valve 15, the outdoor blower 14, and the indoor blowers 22, based on the values detected by the inlet-side refrigerant temperature detection sensors 26, the outlet-side refrigerant temperature detection sensors 27, the refrigerant temperature sensors 43, the intake air temperature sensors 28, and the room temperature sensor 42.

[0069] In this embodiment, the control unit 40 compares the refrigerant temperature inside each indoor heat exchanger 21 detected by the refrigerant temperature sensor 43 with the average value of the inlet-side refrigerant temperature detected by the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature detected by the outlet-side refrigerant temperature detection sensor 27. The control unit 40 then sets the value of the temperature having a larger difference from the set temperature to the reference for controlling the opening degree of the indoor expansion valve 25.

[0070] In other words, in Embodiment 1, control is performed based on the value obtained by adding ΔT to set temperature. However, in this embodiment, the refrigerant temperature can be detected by the refrigerant temperature sensor 43 to acquire the refrigerant temperature in the refrigerant flow path of the indoor heat exchanger 21. This allows a more accurate understanding of the refrigerant state in the indoor heat exchanger 21, enabling accurate control based on the indoor air temperature and refrigerant temperature.

[0071] Since the other parts are the same as in Embodiment 1, the same parts are denoted by the same reference numerals and their description is to be omitted.[2-2. Operation]

[0072] In this embodiment, during heating operation, the control unit 40 acquires the refrigerant temperature inside each indoor heat exchanger 21 detected by the refrigerant temperature sensor 43, the inlet-side refrigerant temperature of the indoor heat exchanger 21 detected by the inlet-side refrigerant temperature detection sensor 26, and the outlet-side refrigerant temperature of the indoor heat exchanger 21 detected by the outlet-side refrigerant temperature detection sensor 27.

[0073] The control unit 40 calculates the average value of the inlet-side refrigerant temperature detected by the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature detected by the outlet-side refrigerant temperature detection sensor 27.

[0074] Based on the calculated average value of the refrigerant temperatures and the refrigerant temperature detected by the refrigerant temperature sensor 43, the control unit 40 sets the value of the temperature having a larger difference from the set temperature to the reference for controlling the opening degree of the indoor expansion valve 25.

[0075] FIG. 5 is a graph showing a relationship between refrigerant temperature and refrigerant flow path position in the indoor heat exchanger 21.

[0076] FIG. 5 shows the change in refrigerant temperature in two indoor heat exchangers 21 with different sizes and heat exchange amounts.

[0077] As shown in FIG. 5, the rate at which the refrigerant temperature drops varies depending on the size and heat exchange amount of the indoor heat exchanger 21.

[0078] In two such indoor heat exchangers 21, the average values of the inlet-side refrigerant temperatures and the outlet-side refrigerant temperatures are the same, but the refrigerant temperature varies depending on the position in the refrigerant flow path inside the indoor heat exchanger 21.

[0079] In this embodiment, the refrigerant temperature is acquired from the refrigerant temperature sensor 43, making it possible to accurately understand the refrigerant temperature inside the indoor heat exchanger 21. This makes it possible to correct the difference in the average value based on the correlation between the size and heat exchange amount of the indoor heat exchanger 21.[2-3. Effects, etc.]

[0080] As described above, in this embodiment, the control unit 40 compares the temperature at a predetermined position in the refrigerant flow path inside the indoor heat exchanger 21 with the temperature of the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature. The control unit 40 then sets the value of the temperature having a larger difference from the set temperature to the reference for controlling the opening degree of the indoor expansion valve 25.

[0081] With this configuration, the control unit 40 can accurately understand the refrigerant temperature inside the indoor heat exchanger 21, making it possible to correct the difference in the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger 21 based on the correlation between the size and the heat exchange amount of the indoor heat exchanger 21. This allows the opening degree of the indoor expansion valve 25 to be controlled based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger 21 and the refrigerant temperature in the refrigerant flow path of the indoor heat exchanger 21, achieving stable heating operation.(Other Embodiments)

[0082] As described above, Embodiment 1 and Embodiment 2 are described as examples of the technique disclosed herein. However, the technique in the present disclosure is not limited to these and can also be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, the components described in Embodiment 1 and Embodiment 2 above can be combined to create new embodiments.

[0083] Note that the above-described embodiments are intended to illustrate the technique in the present disclosure, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.[Configurations supported by the above-described embodiments]

[0084] The above-described embodiments support the following configurations.(Supplementary notes)(Technique 1)

[0085] A refrigeration device including: an outdoor unit including a compressor and an outdoor heat exchanger; a plurality of indoor units positioned in parallel with the outdoor unit, the indoor units each including an indoor heat exchanger, an indoor blower, and an indoor expansion valve, the indoor heat exchanger performing heating operation as a radiator; a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle, wherein each of the indoor units can set an indoor temperature; and a control unit, the control unit setting a control target value for each indoor unit so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger to be a set temperature during heating operation, the control unit adjusting an opening degree of the indoor expansion valve based on the control target value so as to cause the average value to approach the set temperature of each indoor unit.

[0086] With this configuration, the control unit sets the control target value for each indoor unit so as to cause the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger to be the set temperature, and adjusts the opening degree of the indoor expansion valve so as to cause the average value to approach the set temperature of each indoor unit based on the control target value. This makes it possible to provide optimal heating conditions even when refrigerant having a high pressure of a critical pressure or higher is sent to the indoor heat exchanger and the temperature gradient due to the heating load changes. This makes it possible to prevent insufficiently heated air from being blown out of the indoor heat exchanger 21 and perform stable heating operation.(Technique 2)

[0087] The refrigeration device according to Technique 1, wherein the control unit sets the control target value for each indoor unit to a value obtained by adding a predetermined value ΔT to the set temperature.

[0088] With this configuration, the value obtained by adding ΔT to the set temperature is set to the control target value. This allows the capacity of the indoor heat exchanger to be increased depending on the difference between the indoor temperature and the set temperature, and allows the indoor temperature to be controlled to approach the set temperature depending on the difference between the indoor temperature and the set temperature.(Technique 3)

[0089] The refrigeration device according to Technique 2, wherein when a value of ΔT to be added to the set temperature becomes a predetermined value or smaller, the control unit controls the indoor blower to reduce an airflow rate until the value of ΔT exceeds a specified value, and when the value of ΔT exceeds the specified value, the control unit controls the indoor blower to maintain or increase the airflow rate.

[0090] With this configuration, when the value of ΔT becomes a predetermined value or smaller, the airflow rate of the indoor blower is reduced, thereby making it possible to reduce the amount of heat exchanged by the indoor heat exchanger, maintain the temperature of the indoor heat exchanger, and create a state in which the value of ΔT is equal to or larger than a predetermined value. This can prevent the indoor expansion valve from being closed excessively, securing a certain refrigerant flow rate or more. In addition, when the value of ΔT exceeds the predetermined value, the control unit maintains or increases the airflow rate of the indoor blower, making it possible to secure the heat exchange amount in the indoor heat exchanger.(Technique 4)

[0091] The refrigeration device according to Technique 1, wherein the control unit compares a temperature at a midpoint between an inlet and an outlet of each indoor heat exchanger with a temperature of the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature, and sets a value of a temperature having a larger difference from the set temperature to a reference for controlling the opening degree of the indoor expansion valve.

[0092] With this configuration, the control unit can accurately understand the refrigerant temperature inside the indoor heat exchanger, making it possible to correct the difference in the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger based on the correlation between the size of the indoor heat exchanger and the heat exchange amount. This allows the opening degree of the indoor expansion valve to be controlled based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger and the refrigerant temperature in the refrigerant flow path of the indoor heat exchanger, achieving stable heating operation.(Technique 5)

[0093] The refrigeration device according to any one of Techniques 1 to 4, wherein the control unit controls the high pressure of the refrigerant to a supercritical pressure or higher during heating operation of each indoor heat exchanger, and a value of the pressure is determined based on a difference between a temperature of air flowing through the indoor heat exchanger and the set temperature.

[0094] This configuration allows an appropriate amount of refrigerant to be sent to the indoor heat exchanger, preventing refrigerant stagnation in the indoor heat exchanger and minimizing changes in the amount of refrigerant required throughout the year.Industrial Applicability

[0095] The present disclosure is suitable for use in refrigeration devices that can provide optimal heating conditions during heating operation and perform stable heating operation even when using supercritical refrigerants, specifically, in commercial and residential air-conditioning devices.Reference Signs List

[0096] 1air-conditioning device 10outdoor unit 11compressor 12four-way valve 13outdoor heat exchanger 14outdoor blower 15outdoor expansion valve 16, 23fan 17, 24fan motor 20indoor unit 20each indoor unit 21indoor heat exchanger 22indoor blower 25indoor expansion valve 26inlet-side refrigerant temperature detection sensor 27outlet-side refrigerant temperature detection sensor 28intake air temperature sensor 30refrigerant piping 40control unit 41memory unit 42room temperature sensor 43refrigerant temperature sensor

Examples

embodiment 1

(Embodiment 1)

[0014]The following describes Embodiment 1.

[1-1. Configuration]

[1-1-1. Configuration of refrigeration cycle circuit]

[0015]FIG. 1 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1.

[0016]The air-conditioning device 1 includes an outdoor unit 10 and a plurality of indoor units 20 (two in this embodiment). In this embodiment, the air-conditioning device 1 uses carbon dioxide refrigerant as a refrigerant.

[0017]The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor blower 14, and an outdoor expansion valve 15.

[0018]The compressor 11 is, for example, a scroll compressor, which sucks, compresses, and discharges the refrigerant. The four-way valve 12 is a device that communicates with the discharge side of the compressor 11, the suction side of the compressor 11, the outdoor heat exchanger 13, and the high-temperature side refrigerant piping, and is capable of switching the refrig...

embodiment 2

(Embodiment 2)

[0065]The following describes Embodiment 2 of the present disclosure.

[2-1. Configuration]

[0066]FIG. 3 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1 of Embodiment 2. FIG. 4 is a block diagram showing a control configuration of Embodiment 2.

[0067]As shown in FIGS. 3 and 4, in this embodiment, a refrigerant temperature sensor 43 is provided midway through the refrigerant flow path inside each indoor heat exchanger 21.

[0068]In this embodiment, the control unit 40 executes a program stored in the memory unit 41 to control the operation of various devices, such as the compressor 11, the four-way valve 12, the indoor expansion valves 25, the outdoor expansion valve 15, the outdoor blower 14, and the indoor blowers 22, based on the values detected by the inlet-side refrigerant temperature detection sensors 26, the outlet-side refrigerant temperature detection sensors 27, the refrigerant temperature sensors 43, the intake air te...

Technical Field

[0001] The present disclosure relates to a refrigeration device.Background Art

[0002] Patent Literature 1 discloses an air-conditioning device having control means for executing refrigerant amount balance control that adjusts an opening degree of each indoor expansion valve when the air-conditioning device performs heating operation, so as to cause the degree of refrigerant subcooling of each indoor unit to be the average degree of refrigerant subcooling calculated using the maximum value and minimum value of the degree of refrigerant subcooling, or so as to cause the heat exchanger outlet temperature of each indoor unit to be the average heat exchanger outlet temperature calculated using the maximum value and minimum value of the heat exchanger outlet temperature.Citation ListPatent Literature

[0003] Patent Literature 1: Japanese Patent Laid-Open No. 2017-122557Summary of InventionTechnical Problem

[0004] The present disclosure provides a refrigeration device capable of providing optimal heating conditions during heating operation and performing stable heating operation.Solution to Problem

[0005] The refrigeration device in the present disclosure is a refrigeration device including: an outdoor unit including a compressor and an outdoor heat exchanger; a plurality of indoor units positioned in parallel with the outdoor unit, the indoor units each including an indoor heat exchanger, an indoor blower, and an indoor expansion valve, the indoor heat exchanger performing heating operation as a radiator; a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle, wherein each of the indoor units can set an indoor temperature; and a control unit, the control unit setting a control target value for each indoor unit so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger to be a set temperature during heating operation, the control unit adjusting an opening degree of the indoor expansion valve based on the control target value so as to cause the average value to approach the set temperature of each indoor unit.

[0006] This description is intended to include the entire contents of Japanese Patent Application No. 2023-061107, filed on April 5, 2023.Advantageous Effects of Invention

[0007] In the refrigeration device in the present disclosure, the control unit sets the control target value for each indoor unit so as to cause the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger to be the set temperature, and adjusts the opening degree of the indoor expansion valve so as to cause the average value to approach the set temperature of each indoor unit based on the control target value. This makes it possible to provide optimal heating conditions even when refrigerant having a high pressure of a critical pressure or higher is sent to the indoor heat exchanger and the temperature gradient due to the heating load changes. This makes it possible to prevent insufficiently heated air from being blown out of the indoor heat exchanger and perform stable heating operation.Brief Description of the Drawings

[0008] [FIG. 1] FIG. 1 is a refrigeration cycle circuit diagram for an air-conditioning device in Embodiment 1. [FIG. 2] FIG. 2 is a block diagram showing a control configuration in Embodiment 1. [FIG. 3] FIG. 3 is a refrigeration cycle circuit diagram of an air-conditioning device in Embodiment 2. [FIG. 4] FIG. 4 is a block diagram showing a control configuration in Embodiment 2. [FIG. 5] FIG. 5 is a graph showing a relationship between refrigerant temperature and refrigerant flow path position in the indoor heat exchanger in Embodiment 2. Description of Embodiments(Knowledge etc. on which the present disclosure is based)

[0009] At the time when the inventors came up with the present disclosure, one of problems that occur during heating operation using HFC refrigerants was that the refrigerant, when it condenses, would not flow evenly to a plurality of indoor units due to differences in flow path resistances.

[0010] In contrast, when a refrigerant in a supercritical state, such as carbon dioxide refrigerant, is used, condensation does not occur, so that there is not this disadvantage. However, the refrigerant in the indoor heat exchanger undergoes sensible heat change, resulting in a large temperature gradient in the heat exchanger temperature from the inlet toward the outlet of refrigerant. This creates a large temperature difference in the heat exchanger, resulting in an disadvantage of inability to sufficiently heat the blown air. The inventors have discovered this problem and come to create the subject matter of the present disclosure in order to solve this problem.

[0011] The present disclosure therefore provides a refrigeration device capable of providing optimal heating conditions during heating operation and performing stable heating operation.

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed description may be omitted for already well-known matters, or duplicate description may be omitted for substantially the same configurations. This is to avoid the following description from being more redundant than necessary and to facilitate understanding of those skilled in the art.

[0013] Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.(Embodiment 1)

[0014] The following describes Embodiment 1.[1-1. Configuration][1-1-1. Configuration of refrigeration cycle circuit]

[0015] FIG. 1 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1.

[0016] The air-conditioning device 1 includes an outdoor unit 10 and a plurality of indoor units 20 (two in this embodiment). In this embodiment, the air-conditioning device 1 uses carbon dioxide refrigerant as a refrigerant.

[0017] The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor blower 14, and an outdoor expansion valve 15.

[0018] The compressor 11 is, for example, a scroll compressor, which sucks, compresses, and discharges the refrigerant. The four-way valve 12 is a device that communicates with the discharge side of the compressor 11, the suction side of the compressor 11, the outdoor heat exchanger 13, and the high-temperature side refrigerant piping, and is capable of switching the refrigerant flow path.

[0019] The outdoor heat exchanger 13 is, for example, a fin-tube heat exchanger having heat transfer tubes and plate fins, and exchanges heat between the refrigerant flowing inside and the outside air. The outdoor blower 14 is a so-called axial fan that has a fan 16 with multiple blades and a fan motor 17 that rotates the fan 16.

[0020] The four-way valve 12 switches the refrigerant flow path, thereby switching the operation of the air-conditioning device between heating operation, in which the refrigerant in the indoor heat exchanger radiates heat, and cooling operation, in which the refrigerant in the indoor heat exchanger absorbs heat.

[0021] Each indoor unit 20 is a device installed indoors to condition the air therein, and includes an indoor heat exchanger 21 and an indoor blower 22.

[0022] The indoor heat exchanger 21 is, for example, a so-called fin-tube heat exchanger including heat transfer tubes and plate fins.

[0023] The indoor blower 22 is a so-called axial fan including a fan 23 having multiple blades and a fan motor 24 that rotates the fan 23. Note that the indoor blower 22 may use any blower, such as a crossflow fan, sirocco fan, or blower.

[0024] The indoor units 20 are connected in parallel to the outdoor unit 10 via refrigerant piping 30 through which the refrigerant flows.

[0025] The refrigerant piping branches into two parts respectively toward the two indoor units 20, and each of the parts has an indoor expansion valve 25 installed thereon to adjust the refrigerant flow rate and reduce the pressure.

[0026] On the refrigerant inlet-side and the refrigerant outlet-side of each indoor heat exchanger 21 during heating operation, an inlet-side refrigerant temperature detection sensor 26 and an outlet-side refrigerant temperature detection sensor 27 are provided each detecting a corresponding refrigerant temperature.

[0027] Each indoor unit 20 is provided with an intake air temperature sensor 28 that detects the temperature of the intake air sent to the indoor heat exchanger 21. In addition, a room temperature sensor 42 (see FIG. 2) is provided indoors to detect the temperature of the indoor air.[1-1-2. Control configuration]

[0028] Next, a control configuration of the air-conditioning device 1 will be described.

[0029] FIG. 2 is a block diagram showing a control configuration of Embodiment 1.

[0030] As shown in FIG. 2, the air-conditioning device 1 includes a control unit 40. The control unit 40 may be provided in the outdoor unit 10 or may be provided in the indoor units 20.

[0031] The control unit 40 includes a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and a memory unit 41. The memory unit 41 of the control unit 40 has a volatile memory and a non-volatile memory unit. The volatile memory is, for example, RAM (Random Access Memory). The non-volatile memory unit is composed of ROM (Read Only Memory), a hard disk, flash memory, etc. The control unit 40 is also communicatively connected to the various devices of the air-conditioning device 1 via wired communication means such as signal lines, or wireless communication means such as wireless communication circuits.

[0032] The control unit 40 executes a program stored in the memory unit 41 to control the operation of various devices, such as the compressor 11, the four-way valve 12, the indoor expansion valves 25, the outdoor expansion valve 15, the outdoor blower 14, and the indoor blowers 22, based on the values detected by the inlet-side refrigerant temperature detection sensors 26, the outlet-side refrigerant temperature detection sensors 27, the intake air temperature sensors 28, and the room temperature sensor 42.[1-2. Operation]

[0033] Next, operation of the air-conditioning device 1 will be described.

[0034] First, when performing heating operation, the control unit 40 switches the four-way valve 12 in the direction indicated by the dashed line in FIG. 1 and drives the compressor 11.

[0035] Driving the compressor 11 causes the refrigerant to have a high pressure of a critical pressure or higher and to be discharged from the compressor 11. The refrigerant is then sent to each indoor heat exchanger 21 through the refrigerant piping and the four-way valve 12.

[0036] The refrigerant sent to the indoor heat exchanger 21 exchanges heat with the indoor air flowing through the indoor heat exchanger 21, with the indoor blower 22.

[0037] The indoor air is warmed through heat exchange with the refrigerant, and is sent indoors. After heat exchange, the refrigerant temperature drops to approximately the same temperature as the indoor air, and the refrigerant is sent to the outdoor unit 10 through the indoor expansion valve 25.

[0038] The refrigerant sent to the outdoor unit 10 is returned to the compressor 11 through the outdoor expansion mechanism, the outdoor heat exchanger 13, and the four-way valve 12.

[0039] During heating operation of each indoor heat exchanger 21, the control unit 40 controls the high pressure of the refrigerant to a supercritical pressure or higher. A value of the pressure is determined based on the difference between the blow temperature from the intake air temperature sensor 28 of the indoor heat exchanger 21 and a set temperature.

[0040] This allows the appropriate amount of refrigerant to be sent to the indoor heat exchanger 21, preventing refrigerant from stagnation in the indoor heat exchanger 21 and minimizing changes in the amount of refrigerant required throughout the year.

[0041] During heating operation, the control unit 40 acquires the inlet-side refrigerant temperature of each indoor heat exchanger 21 from the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature of the indoor heat exchanger 21 from the outlet-side refrigerant temperature detection sensor 27.

[0042] The control unit 40 calculates the average value of the inlet-side refrigerant temperature from the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature from the outlet-side refrigerant temperature detection sensor 27.

[0043] The control unit 40 sets a control target value for each indoor unit 20 so as to cause the average value of the calculated refrigerant temperatures to be the set temperature, and controls the indoor expansion valve 25 to adjust its opening degree so as to cause the average value to approach the set temperature of each indoor unit 20 based on the control target value.

[0044] In other words, when carbon dioxide refrigerant is used, the refrigerant discharged from the compressor 11 flows into the indoor heat exchangers 21 in a supercritical state. In the case of carbon dioxide refrigerant, heat exchange with the indoor air in each indoor heat exchanger 21 causes a sensible heat change, decreasing the refrigerant temperature to approach that of the indoor air.

[0045] At this time, the amount of refrigerant temperature drop varies depending on the amount of refrigerant flowing through the indoor heat exchanger 21 and the amount of airflow from the indoor blower 22.

[0046] In this embodiment, control is performed based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature so as to cause the average value to have an appropriate temperature difference from the set temperature. This allows the temperature of the indoor heat exchanger 21 to be appropriately controlled even when carbon dioxide refrigerant is used and the temperature gradient from the inlet-side toward the outlet-side of the indoor heat exchanger 21 changes.

[0047] When controlling based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature, the control unit 40 performs control with a control target value obtained by adding ΔT to the set temperature depending on the difference between the indoor air temperature and the set temperature.

[0048] In other words, when the difference between the indoor air temperature and the set temperature is large, control based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature is presumably insufficient. For this reason, control is performed based on the value of ΔT to be added to the set temperature.

[0049] ΔT is set in advance based on indicators such as the temperature difference between the indoor air temperature and the set temperature, the airflow rate made by the indoor blower 22, and the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature. For ΔT, values set in advance are stored in the memory unit 41 as a data table. The control unit 40 reads the required value from the data table in the memory unit 41 and performs control.

[0050] As a result, even when there is a large difference between the indoor temperature and the set temperature, it is possible to control the indoor temperature to approach the set temperature with the optimal amount of heating.

[0051] Furthermore, when the value of ΔT becomes equal to or smaller than a predetermined value, the indoor temperature has approached the set temperature and the amount of heat in the indoor heat exchanger 21 is excessive. Therefore, the control unit 40 first controls the compressor drive frequency to be reduced. Then, the control unit 40 controls the indoor expansion valve 25 to gradually close.

[0052] When the amount of closure of the expansion valve reaches its limit, the control unit 40 controls the airflow rate of the indoor blower 22 to be reduced until ΔT exceeds a specified value.

[0053] In this way, since the refrigerant in the indoor heat exchanger 21 presumably has an excessive amount of heat when the value of ΔT is equal to or smaller than a predetermined value, the compressor drive frequency is controlled to be reduced, the expansion valve is controlled to be closed, and the airflow rate of the indoor blower 22 is controlled to be reduced, making it possible to prevent the expansion valve from closing too much and control the amount of heat of the refrigerant in the indoor heat exchanger 21.

[0054] Furthermore, when the value of ΔT exceeds the specified value, the control unit 40 controls the expansion valve to be open.

[0055] In this way, the expansion valve opening degree is controlled based on whether the ΔT value is equal to or smaller than a predetermined value or greater than the predetermined value. In this case, if the airflow rate of the indoor blower 22 is high, the expansion valve is closed excessively. Therefore, the airflow rate of the indoor blower 22 is controlled in accordance with the opening degree of the expansion valve.

[0056] This allows the expansion valve to keep the opening degree at a predetermined degree or higher while maintaining an appropriate refrigerant heat amount in the indoor heat exchanger 21.[1-3. Effects, etc.]

[0057] As described above, in this embodiment, the refrigeration device includes: an outdoor unit 10 including a compressor 11 and an outdoor heat exchanger 13; a plurality of indoor units 20 positioned in parallel with the outdoor unit 10, the indoor units 20 each including an indoor heat exchanger 21, an indoor blower 22, and an indoor expansion valve 25; and a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle. Each of the indoor units 20 can set an indoor temperature. The refrigeration device includes a control unit 40, the control unit 40 setting a control target value for each indoor unit 20 so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger 21 to be a set temperature during heating operation, the control unit 40 adjusting an opening degree of the indoor expansion valve 25 based on the control target value so as to cause the average value to approach the set temperature of each indoor unit 20.

[0058] According to this configuration, the control unit 40 sets the control target value of each indoor unit 20 to cause the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger 21 to be the set temperature. The control unit 40 then adjusts the opening degree of the indoor expansion valve 25 based on the control target value so as to cause the average value to approach the set temperature of each indoor unit 20. This can provide optimal heating conditions even when refrigerant having a high pressure of a critical pressure or higher is sent to the indoor heat exchanger 21 and the temperature gradient changes due to the heating load. This makes it possible to prevent insufficiently heated air from being blown out of the indoor heat exchanger 21 and perform stable heating operation.

[0059] In this embodiment, the control unit 40 sets the control target value for each indoor unit to a value obtained by adding a predetermined value ΔT to the set temperature.

[0060] With this configuration, the value obtained by adding ΔT to the set temperature is set to the control target value. This allows the capacity made by the indoor heat exchanger 21 to be increased in accordance with the difference between the indoor temperature and the set temperature, and allows the indoor temperature to be controlled to approach the set temperature depending on the difference between the indoor temperature and the set temperature.

[0061] In this embodiment, when the value of ΔT to be added to the set temperature becomes equal to or smaller than a predetermined value, the control unit 40 controls the indoor blower 22 to reduce the airflow rate until the value of ΔT exceeds the specified value, and when the value of ΔT exceeds the specified value, the control unit 40 controls the indoor blower 22 to maintain or increase the airflow rate.

[0062] With this configuration, when the value of ΔT becomes equal to or lower than a predetermined value, the airflow rate of the indoor blower 22 is reduced, thereby making it possible to reduce the amount of heat exchanged by the indoor heat exchanger 21, maintain the temperature of the indoor heat exchanger 21, and create a state in which the value of ΔT is equal to or larger than a predetermined value. This can prevent the indoor expansion valve 25 from being closed excessively, securing a certain refrigerant flow rate or more. In addition, when the value of ΔT exceeds a predetermined value, the control unit 40 maintains or increases the airflow rate of the indoor blower 22, making it possible to secure the heat exchange amount in the indoor heat exchanger 21.

[0063] In this embodiment, during heating operation of each indoor heat exchanger 21, the control unit 40 controls the high pressure of the refrigerant to a supercritical pressure or higher. A value of the pressure is determined based on the difference between the blow temperature from the intake air temperature sensor 28 of the indoor heat exchanger 21 and the set temperature.

[0064] This configuration allows an appropriate amount of refrigerant to be sent to the indoor heat exchanger 21, preventing refrigerant stagnation in the indoor heat exchanger 21 and minimizing changes in the amount of refrigerant required throughout the year.(Embodiment 2)

[0065] The following describes Embodiment 2 of the present disclosure.[2-1. Configuration]

[0066] FIG. 3 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1 of Embodiment 2. FIG. 4 is a block diagram showing a control configuration of Embodiment 2.

[0067] As shown in FIGS. 3 and 4, in this embodiment, a refrigerant temperature sensor 43 is provided midway through the refrigerant flow path inside each indoor heat exchanger 21.

[0068] In this embodiment, the control unit 40 executes a program stored in the memory unit 41 to control the operation of various devices, such as the compressor 11, the four-way valve 12, the indoor expansion valves 25, the outdoor expansion valve 15, the outdoor blower 14, and the indoor blowers 22, based on the values detected by the inlet-side refrigerant temperature detection sensors 26, the outlet-side refrigerant temperature detection sensors 27, the refrigerant temperature sensors 43, the intake air temperature sensors 28, and the room temperature sensor 42.

[0069] In this embodiment, the control unit 40 compares the refrigerant temperature inside each indoor heat exchanger 21 detected by the refrigerant temperature sensor 43 with the average value of the inlet-side refrigerant temperature detected by the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature detected by the outlet-side refrigerant temperature detection sensor 27. The control unit 40 then sets the value of the temperature having a larger difference from the set temperature to the reference for controlling the opening degree of the indoor expansion valve 25.

[0070] In other words, in Embodiment 1, control is performed based on the value obtained by adding ΔT to set temperature. However, in this embodiment, the refrigerant temperature can be detected by the refrigerant temperature sensor 43 to acquire the refrigerant temperature in the refrigerant flow path of the indoor heat exchanger 21. This allows a more accurate understanding of the refrigerant state in the indoor heat exchanger 21, enabling accurate control based on the indoor air temperature and refrigerant temperature.

[0071] Since the other parts are the same as in Embodiment 1, the same parts are denoted by the same reference numerals and their description is to be omitted.[2-2. Operation]

[0072] In this embodiment, during heating operation, the control unit 40 acquires the refrigerant temperature inside each indoor heat exchanger 21 detected by the refrigerant temperature sensor 43, the inlet-side refrigerant temperature of the indoor heat exchanger 21 detected by the inlet-side refrigerant temperature detection sensor 26, and the outlet-side refrigerant temperature of the indoor heat exchanger 21 detected by the outlet-side refrigerant temperature detection sensor 27.

[0073] The control unit 40 calculates the average value of the inlet-side refrigerant temperature detected by the inlet-side refrigerant temperature detection sensor 26 and the outlet-side refrigerant temperature detected by the outlet-side refrigerant temperature detection sensor 27.

[0074] Based on the calculated average value of the refrigerant temperatures and the refrigerant temperature detected by the refrigerant temperature sensor 43, the control unit 40 sets the value of the temperature having a larger difference from the set temperature to the reference for controlling the opening degree of the indoor expansion valve 25.

[0075] FIG. 5 is a graph showing a relationship between refrigerant temperature and refrigerant flow path position in the indoor heat exchanger 21.

[0076] FIG. 5 shows the change in refrigerant temperature in two indoor heat exchangers 21 with different sizes and heat exchange amounts.

[0077] As shown in FIG. 5, the rate at which the refrigerant temperature drops varies depending on the size and heat exchange amount of the indoor heat exchanger 21.

[0078] In two such indoor heat exchangers 21, the average values of the inlet-side refrigerant temperatures and the outlet-side refrigerant temperatures are the same, but the refrigerant temperature varies depending on the position in the refrigerant flow path inside the indoor heat exchanger 21.

[0079] In this embodiment, the refrigerant temperature is acquired from the refrigerant temperature sensor 43, making it possible to accurately understand the refrigerant temperature inside the indoor heat exchanger 21. This makes it possible to correct the difference in the average value based on the correlation between the size and heat exchange amount of the indoor heat exchanger 21.[2-3. Effects, etc.]

[0080] As described above, in this embodiment, the control unit 40 compares the temperature at a predetermined position in the refrigerant flow path inside the indoor heat exchanger 21 with the temperature of the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature. The control unit 40 then sets the value of the temperature having a larger difference from the set temperature to the reference for controlling the opening degree of the indoor expansion valve 25.

[0081] With this configuration, the control unit 40 can accurately understand the refrigerant temperature inside the indoor heat exchanger 21, making it possible to correct the difference in the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger 21 based on the correlation between the size and the heat exchange amount of the indoor heat exchanger 21. This allows the opening degree of the indoor expansion valve 25 to be controlled based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger 21 and the refrigerant temperature in the refrigerant flow path of the indoor heat exchanger 21, achieving stable heating operation.(Other Embodiments)

[0082] As described above, Embodiment 1 and Embodiment 2 are described as examples of the technique disclosed herein. However, the technique in the present disclosure is not limited to these and can also be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. In addition, the components described in Embodiment 1 and Embodiment 2 above can be combined to create new embodiments.

[0083] Note that the above-described embodiments are intended to illustrate the technique in the present disclosure, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.[Configurations supported by the above-described embodiments]

[0084] The above-described embodiments support the following configurations.(Supplementary notes)(Technique 1)

[0085] A refrigeration device including: an outdoor unit including a compressor and an outdoor heat exchanger; a plurality of indoor units positioned in parallel with the outdoor unit, the indoor units each including an indoor heat exchanger, an indoor blower, and an indoor expansion valve, the indoor heat exchanger performing heating operation as a radiator; a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle, wherein each of the indoor units can set an indoor temperature; and a control unit, the control unit setting a control target value for each indoor unit so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger to be a set temperature during heating operation, the control unit adjusting an opening degree of the indoor expansion valve based on the control target value so as to cause the average value to approach the set temperature of each indoor unit.

[0086] With this configuration, the control unit sets the control target value for each indoor unit so as to cause the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger to be the set temperature, and adjusts the opening degree of the indoor expansion valve so as to cause the average value to approach the set temperature of each indoor unit based on the control target value. This makes it possible to provide optimal heating conditions even when refrigerant having a high pressure of a critical pressure or higher is sent to the indoor heat exchanger and the temperature gradient due to the heating load changes. This makes it possible to prevent insufficiently heated air from being blown out of the indoor heat exchanger 21 and perform stable heating operation.(Technique 2)

[0087] The refrigeration device according to Technique 1, wherein the control unit sets the control target value for each indoor unit to a value obtained by adding a predetermined value ΔT to the set temperature.

[0088] With this configuration, the value obtained by adding ΔT to the set temperature is set to the control target value. This allows the capacity of the indoor heat exchanger to be increased depending on the difference between the indoor temperature and the set temperature, and allows the indoor temperature to be controlled to approach the set temperature depending on the difference between the indoor temperature and the set temperature.(Technique 3)

[0089] The refrigeration device according to Technique 2, wherein when a value of ΔT to be added to the set temperature becomes a predetermined value or smaller, the control unit controls the indoor blower to reduce an airflow rate until the value of ΔT exceeds a specified value, and when the value of ΔT exceeds the specified value, the control unit controls the indoor blower to maintain or increase the airflow rate.

[0090] With this configuration, when the value of ΔT becomes a predetermined value or smaller, the airflow rate of the indoor blower is reduced, thereby making it possible to reduce the amount of heat exchanged by the indoor heat exchanger, maintain the temperature of the indoor heat exchanger, and create a state in which the value of ΔT is equal to or larger than a predetermined value. This can prevent the indoor expansion valve from being closed excessively, securing a certain refrigerant flow rate or more. In addition, when the value of ΔT exceeds the predetermined value, the control unit maintains or increases the airflow rate of the indoor blower, making it possible to secure the heat exchange amount in the indoor heat exchanger.(Technique 4)

[0091] The refrigeration device according to Technique 1, wherein the control unit compares a temperature at a midpoint between an inlet and an outlet of each indoor heat exchanger with a temperature of the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature, and sets a value of a temperature having a larger difference from the set temperature to a reference for controlling the opening degree of the indoor expansion valve.

[0092] With this configuration, the control unit can accurately understand the refrigerant temperature inside the indoor heat exchanger, making it possible to correct the difference in the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger based on the correlation between the size of the indoor heat exchanger and the heat exchange amount. This allows the opening degree of the indoor expansion valve to be controlled based on the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature of the indoor heat exchanger and the refrigerant temperature in the refrigerant flow path of the indoor heat exchanger, achieving stable heating operation.(Technique 5)

[0093] The refrigeration device according to any one of Techniques 1 to 4, wherein the control unit controls the high pressure of the refrigerant to a supercritical pressure or higher during heating operation of each indoor heat exchanger, and a value of the pressure is determined based on a difference between a temperature of air flowing through the indoor heat exchanger and the set temperature.

[0094] This configuration allows an appropriate amount of refrigerant to be sent to the indoor heat exchanger, preventing refrigerant stagnation in the indoor heat exchanger and minimizing changes in the amount of refrigerant required throughout the year.Industrial Applicability

[0095] The present disclosure is suitable for use in refrigeration devices that can provide optimal heating conditions during heating operation and perform stable heating operation even when using supercritical refrigerants, specifically, in commercial and residential air-conditioning devices.Reference Signs List

[0096] 1air-conditioning device 10outdoor unit 11compressor 12four-way valve 13outdoor heat exchanger 14outdoor blower 15outdoor expansion valve 16, 23fan 17, 24fan motor 20indoor unit 20each indoor unit 21indoor heat exchanger 22indoor blower 25indoor expansion valve 26inlet-side refrigerant temperature detection sensor 27outlet-side refrigerant temperature detection sensor 28intake air temperature sensor 30refrigerant piping 40control unit 41memory unit 42room temperature sensor 43refrigerant temperature sensor

Examples

embodiment 1

(Embodiment 1)

[0014]The following describes Embodiment 1.

[1-1. Configuration]

[1-1-1. Configuration of refrigeration cycle circuit]

[0015]FIG. 1 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1.

[0016]The air-conditioning device 1 includes an outdoor unit 10 and a plurality of indoor units 20 (two in this embodiment). In this embodiment, the air-conditioning device 1 uses carbon dioxide refrigerant as a refrigerant.

[0017]The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor blower 14, and an outdoor expansion valve 15.

[0018]The compressor 11 is, for example, a scroll compressor, which sucks, compresses, and discharges the refrigerant. The four-way valve 12 is a device that communicates with the discharge side of the compressor 11, the suction side of the compressor 11, the outdoor heat exchanger 13, and the high-temperature side refrigerant piping, and is capable of switching the refrig...

embodiment 2

(Embodiment 2)

[0065]The following describes Embodiment 2 of the present disclosure.

[2-1. Configuration]

[0066]FIG. 3 is a refrigeration cycle circuit diagram of an air-conditioning device (refrigeration device) 1 of Embodiment 2. FIG. 4 is a block diagram showing a control configuration of Embodiment 2.

[0067]As shown in FIGS. 3 and 4, in this embodiment, a refrigerant temperature sensor 43 is provided midway through the refrigerant flow path inside each indoor heat exchanger 21.

[0068]In this embodiment, the control unit 40 executes a program stored in the memory unit 41 to control the operation of various devices, such as the compressor 11, the four-way valve 12, the indoor expansion valves 25, the outdoor expansion valve 15, the outdoor blower 14, and the indoor blowers 22, based on the values detected by the inlet-side refrigerant temperature detection sensors 26, the outlet-side refrigerant temperature detection sensors 27, the refrigerant temperature sensors 43, the intake air te...

Claims

1. A refrigeration device comprising: an outdoor unit including a compressor and an outdoor heat exchanger; a plurality of indoor units positioned in parallel with the outdoor unit, the indoor units each including an indoor heat exchanger, an indoor blower, and an indoor expansion valve, the indoor heat exchanger performing heating operation as a radiator; a refrigerant circuit in which refrigerant, having a high pressure of a critical pressure or higher, circulates through a refrigeration cycle, wherein each of the indoor units can set an indoor temperature; and a control unit, the control unit setting a control target value for each indoor unit so as to cause an average value of an inlet-side refrigerant temperature and an outlet-side refrigerant temperature of each indoor heat exchanger to be a set temperature during heating operation, the control unit adjusting an opening degree of the indoor expansion valve based on the control target value so as to cause the average value to approach the set temperature of each indoor unit.

2. The refrigeration device according to claim 1, wherein the control unit sets the control target value for each indoor unit to a value obtained by adding a predetermined value ΔT to the set temperature.

3. The refrigeration device according to claim 2, wherein when a value of ΔT to be added to the set temperature becomes a predetermined value or smaller, the control unit controls the indoor blower to reduce an airflow rate until the value of ΔT exceeds a specified value, and when the value of ΔT exceeds the specified value, the control unit controls the indoor blower to maintain or increase the airflow rate.

4. The refrigeration device according to claim 1, wherein the control unit compares a temperature at a midpoint between an inlet and an outlet of each indoor heat exchanger with a temperature of the average value of the inlet-side refrigerant temperature and the outlet-side refrigerant temperature, and sets a value of a temperature having a larger difference from the set temperature to a reference for controlling the opening degree of the indoor expansion valve.

5. The refrigeration device according to claim 1, wherein the control unit controls the high pressure of the refrigerant to a supercritical pressure or higher during heating operation of each indoor heat exchanger, and a value of the pressure is determined based on a difference between a temperature of air flowing through the indoor heat exchanger and the set temperature.

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