EP3502593A1

EP3502593A1 - Composition abnormality detection device and composition abnormality detection method

Info

Publication number: EP3502593A1
Application number: EP18757070.0A
Authority: EP
Inventors: Atsushi Enya
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2017-02-27
Filing date: 2018-02-21
Publication date: 2019-06-26
Also published as: JP2018141574A; WO2018155513A1; EP3502593A4

Abstract

In order to detect abnormalities such as slow refrigeration leaks at a relatively early stage, this composition abnormality detection unit (60) is provided with: multiple temperature sensors disposed from a refrigerant inlet to a refrigerant outlet of a condenser; a pressure sensor which detects the inlet-side pressure of the condenser; a reference value calculation unit (61) which uses the detected pressure value detected by the pressure sensor to calculate a reference value of the temperature gradient in the condenser; a temperature gradient calculation unit (62) which uses multiple detected temperature values detected by the temperature detection unit to calculate the temperature gradient; and an abnormality determination unit (63) which determines an abnormality if the difference between the temperature gradient calculated by the temperature gradient calculation unit (62) and the reference value of the temperature gradient calculated by the reference value calculation unit (61) is outside of a prescribed temperature range.

Description

Technical Field

The present invention relates to a composition abnormality detection device and a composition abnormality detection method.

Background Art

In related art, a refrigerant of a refrigeration cycle includes a refrigerant of a single composition and a mixed refrigerant obtained by mixing a plurality of refrigerants. The mixed refrigerant includes an azeotropic mixed refrigerant and a nonazeotropic mixed refrigerant.
In the nonazeotropic mixed refrigerant, boiling points of mixed compositions are different from each other, and thus, in a condensation process, the nonazeotropic mixed refrigerant is liquefied from a refrigerant having a high boiling point. Accordingly, a liquid phase in a receiver or an accumulator contains a lot of refrigerant having a high boiling point. Accordingly, in a refrigeration system using the nonazeotropic mixed refrigerant, a composition ratio when the refrigerant is enclosed and a composition ratio (hereinafter, referred to as a "circulation composition") when the refrigeration system is operated are different from each other, and thus, it is important to perform an appropriate control using thermo-physical properties of the refrigerant corresponding to the circulation composition.
For example, PTL 1 discloses a refrigeration device in which a plurality of temperature measurement means are provided from a refrigerant inlet to a refrigerant outlet in an internal heat exchanger, a temperature glide of the internal heat exchanger is calculated from a temperature measured by the temperature measurement means, dryness of an inlet of the internal heat exchanger is calculated from the temperature glide, and an opening degree of an expansion valve, a frequency of a compressor, and a rotation speed of a fan are adjusted by the calculated dryness.

Citation List

Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 2015-141005

Summary of Invention

Technical Problem

In a case where leakage of a refrigerant occurs, a circulation composition is changed. In a case where a large amount of refrigerant leaks at once, operation characteristics are largely changed, and thus, it is possible to easily detect the leakage of the refrigerant. However, in a case where a small amount of refrigerant leaks over a certain time such as slow leakage, even when the circulation composition is changed by changes of thermodynamic characteristics, the appropriate control disclosed in PTL 1 is performed, and maintenance of performance is possible. In this case, there is a possibility that it may be mistaken as performance deterioration or the like due to general aged deterioration, and thus, it is difficult to detect the slow leakage.
The present invention is made in consideration of the above-described circumstances, and an object thereof is to provide a composition abnormality detection device and a composition abnormality detection method capable of detecting an abnormality of slow leakage or the like of a refrigerant at a relatively early stage.

Solution to Problem

According to a first aspect of the present invention, there is provided a composition abnormality detection device which is applied to a refrigerant circuit using a nonazeotropic mixed refrigerant obtained by mixing a plurality kinds of refrigerants having different boiling points, the device including: a plurality of temperature measurement units which are provided from a refrigerant inlet to a refrigerant outlet of a condenser; a pressure measurement unit which measures an inlet-side pressure of the condenser; a reference value calculation unit which calculates a reference value of a temperature gradient in the condenser using a pressure measurement value measured by the pressure measurement unit; a temperature gradient calculation unit which calculates the temperature gradient using a plurality of temperature measurement values measured by the temperature measurement units; and an abnormality determination unit which determines an abnormality in a case where a difference between the temperature gradient calculated by the temperature gradient calculation unit and the reference value of the temperature gradient calculated by the reference value calculation unit is outside a preset temperature range.
The temperature gradients in the condenser are different from each other according to the composition ratio, and thus, it is possible to ascertain a change of the composition ratios of the refrigerant based on the temperature gradient. The temperature gradient is changed according to a pressure. Accordingly, in the present aspect, it is possible to ascertain the change of the composition ratio by comparing a current temperature gradient and a temperature gradient according to the composition ratio when the refrigerant is enclosed under the same pressure condition with each other.
According to the composition abnormality detection device, the plurality of temperature measurement units are provided from the refrigerant inlet to the refrigerant outlet of the condenser, and the temperature gradient corresponding to the current composition ratio is calculated using the plurality of temperature measurement values measured by the plurality of temperature measurement units by the temperature gradient calculation unit. The inlet-side pressure of the condenser is measured by the pressure measurement unit, and the reference value of the temperature gradient in the condenser is calculated by the reference value calculation unit using the pressure measurement value measured by the pressure measurement unit. The reference value is a theoretical value of the temperature gradient corresponding to the composition ratio when the refrigerant is enclosed under the same pressure conditions. In addition, whether or not the difference between the temperature gradient calculated by the temperature gradient calculation unit and the reference value of the temperature gradient calculated by the reference value calculation unit is outside the preset temperature range is determined by the abnormality determination unit, and in a case where the difference is outside the temperature range, the abnormality is determined. Therefore, according to the composition abnormality detection device of the present aspect, the abnormality is determined according to the change in the composition ratio, and thus, even in the slow leakage or the like in which the composition ratio is gradually changed, it is possible to detect the leakage at a relatively early stage.
In the condenser, an outdoor heat exchanger functions as the condenser in a case of a cooling operation, and an indoor heat exchanger functions as the condenser in a case of a heating operation.
In the composition abnormality detection device, in a case where an effective length of a refrigerant pipe from the refrigerant inlet to the refrigerant outlet of the condenser is defined as 100%, a start position of the effective length is defined as 0%, and an end position of the effective length is defined as 100%, the temperature measurement unit may include at least one inlet-side temperature measurement unit which is provided at the effective length of 0% to 40% and at least one outlet-side temperature measurement unit which is provided at the effective length of 90% to 100%, and the temperature gradient calculation unit may calculate the temperature gradient using a temperature measurement value measured by at least one inlet-side temperature measurement unit and a temperature measurement value measured by at least one outlet-side temperature measurement unit.
The temperature measurement unit includes a predetermined accuracy error. For example, an inexpensive temperature sensor such as a copper pipe type thermistor used in the refrigeration device has a simple structure, and thus, the accuracy error of approximately ±2.0°C may occur. In this case, when the temperature gradient is equal to or less than 4°C, it is difficult to determine whether the calculated temperature gradient is a value generated from the refrigerant composition or a value generated by a sensor error. However, for example, the temperature gradient is calculated using the temperature measurement values measured by the inlet-side temperature measurement unit which is provided at the effective length of 0% to 40% and the outlet-side temperature measurement unit which is provided at the effective length of 90% to 100%, and thus, it is possible to secure the temperature gradient of 4°C or more, and it is possible to use the inexpensive temperature sensor.
In the composition abnormality detection device, the temperature gradient calculation unit may calculate, as the temperature gradient, a difference between a temperature measurement value measured by the inlet-side temperature measurement unit closest to the start position and a lowest temperature measurement value of temperature measurement values measured by other temperature measurement units.
In this way, the difference between the highest temperature measurement value measured by the inlet-side temperature measurement unit and the lowest temperature measurement value of temperature measurement values measured by other temperature measurement units is calculated as the temperature gradient, and thus, it is possible to detect the abnormality using the maximum temperature gradient which can be calculated. Therefore, it is possible to decrease influences generated by the sensor error, and it is possible to the temperature gradient corresponding to the composition ratio.
According to a second aspect of the present inventio n, there is provided a refrigeration device using a nonaze otropic mixed refrigerant having the composition abnormali ty detection device.
According to a third aspect of the present invention, there is provided a composition abnormality detection method which is applied to a refrigerant circuit using a nonazeotropic mixed refrigerant obtained by mixing a plurality kinds of refrigerants having different boiling points, the method including: a step of measuring a temperature at a plurality of temperature measurement positions provided from a refrigerant inlet to a refrigerant outlet of a condenser; a step of calculating a temperature gradient in the condenser using temperature measurement values at a plurality of measurement positions of the condenser; a step of measuring an inlet-side pressure of the condenser; a step of calculating a reference value of the temperature gradient from the inlet-side pressure of the condenser; and a step of determining an abnormality in a case where a difference between the calculated temperature gradient and the reference value of the temperature gradient is outside a preset temperature range.
According to a fourth aspect of the present invention, there is provided a composition abnormality detection device which includes a condenser, an evaporator, a receiver which is provided between the condenser and the evaporator, and a decompression unit which is provided between the receiver and the evaporator, and is applied to a refrigerant circuit using a nonazeotropic mixed refrigerant obtained by mixing a plurality kinds of refrigerants having different boiling points, the device including: a first temperature measurement unit which measures a temperature of a refrigerant flowing through a portion between the condenser and the receiver; a second temperature measurement unit which measures a temperature of a refrigerant decompressed by the decompression unit; a pressure measurement unit which measures a pressure of the refrigerant decompressed by the decompression unit; a first enthalpy calculation unit which calculates a first enthalpy of a cooling region from a first temperature measured by the first temperature measurement unit; a first change amount calculation unit which calculates, as a first change amount, a change amount between a latest first enthalpy calculated by the first enthalpy calculation unit and a first enthalpy corresponding to a composition ratio of the refrigerant when the refrigerant is enclosed; a second enthalpy calculation unit which calculates, as a second enthalpy, an enthalpy after the decompression using a second temperature measured by the second temperature measurement unit and a pressure measured by the pressure measurement unit; a second change amount calculation unit which calculates, as a second change amount, a change amount of the second enthalpy between a latest second enthalpy calculated by the second enthalpy calculation unit and the second enthalpy corresponding to the composition ratio of the refrigerant when the refrigerant is enclosed; and an abnormality determination unit which determines an abnormality in a case where the first change amount calculated by the first change amount calculation unit or the second change amount calculated by the second change amount calculation unit is equal to or more than a predetermined threshold value which is set in advance.

Advantageous Effects of Invention

According to the present invention, it is possible to detect an abnormality such as slow leakage of a refrigerant at a relatively early stage.

Brief Description of Drawings

Fig. 1 is a diagram showing a schematic refrigerant circuit of a refrigeration device having a composition abnormality detection device according to a first embodiment of the present invention.
Fig. 2 is a diagram showing a schematic configuration of an outdoor heat exchanger according to the first embodiment of the present invention.
Fig. 3 is a diagram showing a schematic configuration of an indoor heat exchanger according to the first embodiment of the present invention.
Fig. 4 is a functional block diagram of a controller according to the first embodiment of the present invention.
Fig. 5 is a graph showing an example of a temperature gradient of a nonazeotropic mixed refrigerant obtained by mixing two kinds of refrigerants.
Fig. 6 is a graph showing an example of a temperature gradient of a nonazeotropic mixed refrigerant obtained by mixing three kinds of refrigerants.
Fig. 7 is a diagram showing a schematic refrigerant circuit of a refrigeration device having a composition abnormality detection device according to a second embodiment of the present invention.
Fig. 8 is a functional block diagram of a controller according to the second embodiment of the present invention.
Fig. 9 is a Mollier diagram showing a relationship between a first enthalpy and a second enthalpy. Description of Embodiments

[First Embodiment]

Hereinafter, a composition abnormality detection device and a composition abnormality detection method according to a first embodiment of the present invention will be described with reference to the accompanying drawings.
Fig. 1 is a diagram showing a schematic refrigerant circuit of a refrigeration device having the composition abnormality detection device according to the present embodiment. This refrigeration device 1 includes a compressor 2, a four-way switching valve (flow path switching unit) 4 which switches a refrigerant circulation direction, an outdoor heat exchanger 6 in which a blower 5 is provided, an electronic expansion valve 7 for heating, a receiver 8, an electronic expansion valve 9 for cooling, an indoor heat exchanger 11 in which a blower 10 is provided, and a closed cycle refrigerant circuit which sequentially connects an accumulator 12 provided in a suction pipe of the compressor 2 to a refrigerant pipe.
In the refrigeration device 1, the refrigerant circulation direction is switched by the four-way switching valve 4, and thus, a heat pump cycle in which cooling and heating can be performed is realized. However, the refrigeration device 1 may be configured of a single cycle having a cooling pump or a heat pump.
In the refrigeration device 1, a high-temperature and high-pressure refrigerant gas discharged from the compressor 2 is circulated to the outdoor heat exchanger 6 side by the four-way switching valve 4, the outdoor heat exchanger 6 functions as a condenser, the indoor heat exchanger 11 functions as an evaporator, and thus, a cooling operation is performed. The high-temperature and high-pressure refrigerant gas is circulated to the indoor heat exchanger 11 side by the four-way switching valve 4, the indoor heat exchanger 11 functions as the condenser, the outdoor heat exchanger 6 functions as the evaporator, and thus, a heating operation can be performed.
A nonazeotropic mixed refrigerant is enclosed in the refrigeration device 1. As an example of nonazeotropic mixed refrigerant, there is a refrigerant obtained by mixing CO₂ (carbon dioxide), R32 (HFC32), R1234ze (HFO1234ze) with each other at a predetermined ratio.
In the refrigeration device 1, a supercooler 13 for further supercooling a refrigerant flowing out from the outdoor heat exchanger 6 during the cooling operation is provided on a downstream side of the outdoor heat exchanger 6. In this way, the supercooler 13 is provided, it is possible to reliably condense a refrigerant having a low boiling point, and it is possible to improve a refrigeration capacity.
A supercooler (not shown) for further supercooling a refrigerant flowing out from the indoor heat exchanger 11 during the heating operation is provided on a downstream side of the indoor heat exchanger 11.
In the outdoor heat exchanger 6, a pressure sensor (pressure measurement unit) 30a is provided on a refrigerant flow inlet side at the time of the cooling operation.
In addition, a plurality of temperature sensors (temperature measurement unit) 31a to 34a are provided in the outdoor heat exchanger 6. Here, a case where four temperature sensors are provided is exemplified. However, the number of temperature sensors are not limited to this example.
Fig. 2 is a diagram showing a schematic configuration of the outdoor heat exchanger 6.
As shown in Fig. 2, for example, the outdoor heat exchanger 6 according to the present embodiment is a shell and tube type heat exchanger and is configured such that the refrigerant flows through a plurality of heat transfer pipes (refrigerant pipes) 40a to 40n provided inside a main body of the outdoor heat exchanger 6.
At the time of the cooling operation, the refrigerant flows from a refrigerant inlet 21a into the main body, the refrigerant is heat-exchanged with cooling water flowing through the main body in a process in which the refrigerant flows through the heat transfer pipes 40a to 40n so as to be condensed, and thus, the refrigerant flows out from a refrigerant outlet 22a as a liquid refrigerant or a gas-liquid mixed refrigerant.
In Fig. 2, a case where the plurality of heat transfer pipes 40a to 40n are provided between the refrigerant inlet 21a to the refrigerant outlet 22a is exemplified. However, the number of the installed heat transfer pipes is not particularly limited. For example, only one heat transfer pipe 40a may be provided.
The temperature sensors 31a to 34a are provided in at least one heat transfer pipe 40a out of the plurality of heat transfer pipes 40a to 40n. Specifically, in a case where an effective length of a refrigerant pipe from the refrigerant inlet 21a to the refrigerant outlet 22a is defined as 100%, a start position of the effective length is defined as 0%, and an end position of the effective length is defined as 100%, the temperature sensor 31a is provided at a position of approximately 0%, the temperature sensor 32a is provided at a position of approximately 10%, the temperature sensor 33a is provided at a position of approximately 20%, and the temperature sensor 34a is provided at a position of approximately 90%.
The installation positions of the temperature sensors 31a to 34a are not particularly limited to this example. However, for example, preferably, at least one temperature sensor (inlet-side temperature measurement unit) is provided at the effective length of 0% to 40%, and at least one temperature sensor (outlet-side temperature measurement unit) is provided at the effective length of 90% to 100%. According to this disposition, it is possible to secure a temperature gradient of 5°C or more. An inexpensive temperature sensor may include a measurement error of approximately 4°C. In a case where the inexpensive temperature sensor is used, when an actual temperature gradient is approximately 4°C, it is difficult to accurately calculate the temperature gradient from a value measured by the temperature sensor. However, each temperature sensor is disposed at the position at which the temperature gradient of at least 4°C or more is obtained, and thus, it is possible to use the inexpensive temperature sensor.
Similarly, in the indoor heat exchanger 11, temperature sensors 31b to 34b are provided at the same position as that of the above-described outdoor heat exchanger 6. Fig. 3 is a diagram showing a schematic configuration of the indoor heat exchanger 11. As shown in Fig. 3, for example, the indoor heat exchanger 11 according to the present embodiment is a shell and tube type heat exchanger and is configured such that a refrigerant flows through a plurality of heat transfer pipes (refrigerant pipes) 41a to 41n provided inside a main body of the indoor heat exchanger 11.
At the time of heating operation, the refrigerant flows from a refrigerant inlet 21b into the main body, the refrigerant is heat-exchanged with cooling water or air flowing through the main body in a process in which the refrigerant flows through the heat transfer pipes 41a to 41n so as to be condensed, and thus, the refrigerant flows out from a refrigerant outlet 22b as a liquid refrigerant or a gas-liquid mixed refrigerant.
In Fig. 3, a case where the plurality of heat transfer pipes 41a to 41n are provided between the refrigerant inlet 21b to the refrigerant outlet 22b is exemplified. However, the number of the installed heat transfer pipes is not particularly limited. For example, only one heat transfer pipe 41a may be provided.
The temperature sensors 31b to 34b are provided in at least one heat transfer pipe 41a out of the plurality of heat transfer pipes 41a to 41n. Specifically, in a case where an effective length of a refrigerant pipe from the refrigerant inlet 21b to the refrigerant outlet 22b is defined as 100%, a start position of the effective length is defined as 0%, and an end position of the effective length is defined as 100%, the temperature sensor 31b is provided at a position of approximately 0%, the temperature sensor 32b is provided at a position of approximately 10%, the temperature sensor 33b is provided at a position of approximately 20%, and the temperature sensor 34b is provided at a position of approximately 90%.
The installation positions of the temperature sensors 31b to 34b are not particularly limited to this example. However, for example, preferably, at least one temperature sensor (inlet-side temperature measurement unit) is provided at the effective length of 0% to 40%, and at least one temperature sensor (outlet-side temperature measurement unit) is provided at the effective length of 90% to 100%. According to this disposition, it is possible to secure a temperature gradient of 5°C or more. An inexpensive temperature sensor may include the measurement error of approximately 4°C. In a case where the inexpensive temperature sensor is used, when an actual temperature gradient is approximately 4°C, it is difficult to accurately calculate the temperature gradient from a value measured by the temperature sensor. However, each temperature sensor is disposed at the position at which the temperature gradient of at least 4°C or more is obtained, and thus, it is possible to use the inexpensive temperature sensor.
Pressure measurement values measured by the pressure sensors 30a and 30b and temperature measurement values measured by the temperature sensors 31a to 34a and 30b to 34b are output to a controller 50 (refer to Fig. 4).
The controller 50 controls all operations of the refrigeration device 1, and for example, as shown in Fig. 4, includes a compressor control unit (not shown) which controls an operating frequency of a compressor, an expansion valve control unit (not shown) which controls an opening degree of an expansion valve, a blower control unit (not shown) which controls a rotation speed of a blower, or the like in addition to a composition abnormality detection unit (composition abnormality detection device) 60.
For example, the controller 50 includes a Central Processing Unit (CPU) (not shown), a Random Access Memory (RAM) (not shown), a computer readable recording medium (not shown), or the like. A series of processing steps for realizing functions of the above-described portions are recorded in a recording medium or the like in the form of a program, the CPU reads this program using the RAM or the like and executes processing/calculation processing of information, and thus, various functions to be described later are realized.
At the time of the cooling, the composition abnormality detection unit 60 detects a change of a composition ratio based on the temperature gradient in a condensation process in the outdoor heat exchanger 6 functioning as the condenser, and at the time of the heating, the composition abnormality detection unit 60 detects the change of the composition ratio based on the temperature gradient in the condensation process in the indoor heat exchanger 11 functioning as the condenser.
Hereafter, the detection of the composition change at the time of the cooling will be described as an example.
For example, as shown in Figs. 5 and 6, the temperature gradient in the outdoor heat exchanger 6 has unique characteristics according to the composition ratio. Fig. 5 is a graph showing an example of a temperature gradient of a nonazeotropic mixed refrigerant obtained by mixing two kinds of refrigerants (for example, R1234ze and R32), a horizontal axis indicates the composition ratio, and a vertical axis indicates the temperature gradient. In Fig. 5, a characteristic A indicates the temperature gradient at positions of the effective lengths 0% and 100%, a characteristic B indicates the temperature gradient at positions of the effective lengths 10% and 90%, and a characteristic C indicates the temperature gradient at positions of the effective lengths 20% and 90%, a characteristic D indicates the temperature gradient at the positions of the effective lengths 30% and 90%, a characteristic E indicates the temperature gradient at positions of the effective lengths 40% and 90%, and a characteristic F indicates the temperature gradient at positions of the effective lengths 50% and 90%.
Fig. 6 is a graph showing an example of a temperature gradient of a nonazeotropic mixed refrigerant obtained by mixing three kinds of refrigerants (for example, R1234ze, R32, and CO₂), and each side of a triangle indicates a mixing ratio of each refrigerant. The temperature gradient is changed according to the pressure.
In the present embodiment, a current temperature gradient in the outdoor heat exchanger 6 and a temperature gradient according to a composition ratio when the refrigerant is enclosed under the same pressure condition are compared with each other, and thus, the change of the composition ratio with respect to the time of the enclosure of the refrigerant is determined so as to detect a composition abnormality.
Specifically, the composition abnormality detection unit 60 includes a reference value calculation unit 61, a temperature gradient calculation unit 62, and an abnormality determination unit 63. The reference value calculation unit 61 calculates a reference value of the temperature gradient in the outdoor heat exchanger 6 using the pressure measured by the pressure sensor 30a. Specifically, first, the reference value calculation unit 61 obtains a saturation gas temperature Tsg and a saturation liquid temperature Tsl from the pressure measured by the pressure sensor 30a. For example, the saturation gas temperature Tsg and the saturation liquid temperature Tsl relate to the enclosed refrigerant composition, and may be obtained by holding a conversion expression for converting the pressure to the saturation gas temperature and a conversion expression for converting the pressure to the saturation liquid temperature in advance and by using the conversion expression. A table in which the pressure and the saturation gas temperature are associated with each other and a table in which the pressure and the saturation liquid temperature are associated with each other may be prepared in advance so as to be held.
Next, the reference value calculation unit 61 calculates a theoretical value of the temperature gradient from a difference between the acquired saturation gas temperature Tsg and saturation liquid temperature Tsl, and an absolute value of the theoretical value is set to a reference value ΔTp. That is, the reference value is represented by the following Expression (1). $Δ Tp = | Tsg - Tsl |$
The temperature gradient calculation unit 62 calculates the temperature gradient using the plurality of temperature measurement values measured by the temperature sensors 31a to 34a. For example, the temperature gradient calculation unit 62 extracts a smallest measurement value Min (Th2 to Th4) from measurement values Th2 to Th4 measured by the temperature sensors 32a to 34a and calculates a difference between the extracted measurement value Min (Th2 to Th4) and the measurement value Th1 measured by the temperature sensor 31a, and an absolute value of the difference is set to a temperature gradient ΔTt. For example, the temperature gradient is represented by the following Expression (2). $Δ Tt = | Th 1 - Min (Th) (2 toTh 4) |$
A calculation method of the temperature gradient is an example, and the temperature gradient may be calculated using the measurement values of two temperature sensors which are set in advance. For example, a difference between the measurement value Th1 of the temperature sensor 31a and the measurement value Th4 of the temperature sensor 34a is calculated, and an absolute value of the difference may be set to the temperature gradient ΔTt. In this case, the temperature gradient is presented by the following Expression (3). $Δ Tt = | Th 1 - Th 4 |$
The abnormality determination unit 63 determines an abnormality in a case where a difference between the temperature gradient ΔTt calculated by the temperature gradient calculation unit 62 and the reference value ΔTp of the temperature gradient calculated by the reference value calculation unit 61 is outside a preset temperature range.
In a case where the abnormality is determined by the abnormality determination unit 63, it is determined that the refrigerant composition before the refrigerant is enclosed is changed to exceed an allowable range, an alarm unit notifies an error. For example, the notification of the error may be performed by lighting an LED or the like provided in an indoor unit, and in a case where a display unit or the like is provided, an error message or the like may be displayed on the display unit such that the error is notified. In addition to the visual alarm unit, a sound or a message notifying an error may be issued from a speaker or the like.
In a case where the abnormality is not determined by the abnormality determination unit 63, that is, in a case where the difference between the temperature gradient ΔTt and the reference value ΔTp is within the preset temperature range, the operating frequency of the compressor 2, the opening degree of the electronic expansion valve 9 for the cooling, the rotation speeds of the blowers 5 and 10, or the like may be adjusted based on the results. Accordingly, in a range in which the abnormality is not determined, a control of the refrigeration device 1 corresponding to the circulation composition is performed, and thus, it is possible to suppress a decrease in a refrigeration capacity generated by a change of the circulation composition.
Similarly, at the time of the heating operation, the indoor heat exchanger 11 functions as the condenser, and thus, similar processing is performed using temperature measurement values measured by the temperature sensors 31b to 34b provided in the indoor heat exchanger 11 instead of the temperature sensors 31a to 31d and the pressure measurement value measured by the pressure sensor 30b instead of the pressure sensor 30a, and thus, it is possible to detect the change of the composition ratio.
As described above, according to the composition abnormality detection unit (composition abnormality detection device) 60, the composition abnormality detection method, and the refrigeration device 1 of the present embodiment, the current temperature gradient and the reference value which is the theoretical value of the temperature gradient corresponding to the composition ratio when the refrigerant is enclosed are compared with each other under the same pressure condition, in the case where the difference is outside the preset temperature range, the abnormality is determined. In this way, the composition abnormality is determined according to the change in the composition ratio, and thus, even in slow leakage or the like in which the composition ratio is gradually changed, it is possible to detect the leakage at a relatively early stage.
In the present embodiment, in the outdoor heat exchanger 6 and the indoor heat exchanger 11 (condenser), the temperature sensors 31a to 33a (31b to 33b) are disposed at the effective length of the refrigerant pipe of 0% to 40%, the temperature sensor 34a (34b) is disposed at the effective length of 90% to 100%, the difference between the temperature measurement value measured by the temperature sensor 31a (31b) and the lowest temperature measurement value of the temperature measurement values measured by the temperature sensors 32a to 34a (32b to 34b) is calculated as the temperature gradient, and thus, the temperature gradient of at least 4°C or more can be obtained. Accordingly, even in a case where an inexpensive temperature sensor having an accuracy error of approximately ±2.0°C is used, it is possible to determine the calculated temperature gradient is a value depending on the refrigerant composition or a value generated by the sensor error.
As shown in Fig. 5, in the case of the mixed refrigerant having two kinds of refrigerants obtained by mixing two kinds of refrigerants with each other, the characteristic of temperature gradient is held in advance, and thus, it is possible to obtain the composition ratio of the refrigerant from the temperature gradient calculated by the temperature gradient calculation unit 62.
In the present embodiment, the pressure sensors 30a and 30b are provided as the pressure sensor used to detect a composition abnormality described later. However, instead of the pressure sensors 30a and 30b, a pressure sensor for cooling and heating may be installed between the compressor 2 and the four-way switching valve 4.

[Second Embodiment]

Next, a composition abnormality detection device, a composition abnormality detection method, and a refrigeration device according to a second embodiment of the present invention will be described. In the following descriptions, the same reference numerals are assigned to the same configurations as those of the first embodiment, detail descriptions thereof are omitted, and different matters therebetween are mainly described.
Fig. 7 is a diagram showing a schematic refrigerant circuit of a refrigeration device 1' having a composition abnormality detection device according to the present embodiment. As shown in Fig. 7, the refrigeration device 1' according to the present embodiment includes the refrigerant circuit which is the same as that of the above-described first embodiment. However, in the present embodiment, installation locations of the temperature sensor and the pressure sensor and the method for detecting the composition abnormality are different from those of the first embodiment.
That is, in the refrigeration device 1' according to the present embodiment, a temperature sensor (first temperature measurement unit) 35 for measuring the temperature of the refrigerant flowing through a portion between the outdoor heat exchanger 6 and the receiver 8, a temperature sensor (second temperature measurement unit) 36 for measuring the temperature of the refrigerant which is decompressed by the cooling electronic expansion valve 9, and a pressure sensor (pressure measurement unit) 37 for measuring the pressure of the refrigerant which is decompressed by the cooling electronic expansion valve 9 are provided. Moreover, the composition abnormality is detected based on measurement values of the temperature sensors 35 and 36 and the pressure sensor 37.
For example, in a case where the composition ratio of the refrigerant is not changed, an enthalpy (hereinafter, referred to as a "first enthalpy") H(Th1) of the refrigerant flowing out from the outdoor heat exchanger 6 and an enthalpy (hereinafter, referred to as a "second enthalpy") H(Th2) of the refrigerant which is decompressed by the cooling electronic expansion valve 9 are theoretically coincident with each other as shown in a Mollier diagram of Fig. 9.
However, in a case where the composition ratio is changed, the first enthalpy and the second enthalpy are deviated from a theoretical value. Accordingly, it is possible to detect the composition abnormality based on an amount of deviation of the enthalpy.
Fig. 8 is a functional block diagram of a controller 50' according to the present embodiment. As shown in Fig. 8, the controller 50' of the present embodiment includes a composition abnormality detection unit 70. The composition abnormality detection unit 70 includes a first enthalpy calculation unit 71, a first change amount calculation unit 72, a second enthalpy calculation unit 73, a second change amount calculation unit 74 and an abnormality determination unit 75.
The first enthalpy calculation unit 71 calculates the enthalpy of a cooling region from a first temperature measured by the temperature sensor 35. For example, the first enthalpy calculation unit 71 stores a Mollier diagram or other similar information which corresponds to the composition ratio of the refrigerant when the refrigerant is enclosed. The first enthalpy calculation unit 71 obtains the enthalpy corresponding to the first temperature from the Mollier diagram or other similar information, which is stored in advance, and sets this enthalpy as the first enthalpy H(Th1)'.
The first change amount calculation unit 72 calculates a change amount between a latest first enthalpy H(Th1)' calculated by the first enthalpy calculation unit 71 and the theoretical value of the first enthalpy corresponding to the refrigerant composition ratio when the refrigerant is enclosed, that is, the first enthalpy H(Th1) shown in Fig. 9, as the first change amount.
The second enthalpy calculation unit 73 calculates the enthalpy after the decompression as the second enthalpy H(Th2)' using the second temperature measured by the temperature sensor 36 and the pressure measured by the pressure sensor 37. Specifically, the second enthalpy calculation unit 73 calculates the enthalpy H(Th2)' of the refrigerant decompressed by the cooling electronic expansion valve 9 using the following Expression (4). $H (Th) (2)' = HG \times x + HL \times (1 - x)$
In Expression (4), HG indicates a saturation gas enthalpy after the decompression, and HL indicates a saturation liquid enthalpy after the decompression.
The second change amount calculation unit 74 calculates a change amount between a latest second enthalpy H(Th2)' calculated by the second enthalpy calculation unit 73 and a second enthalpy H(Th2) corresponding to the refrigerant composition ratio when the refrigerant is enclosed, as the second change amount. Here, as shown in Fig. 9, the theoretical value H(Th2) of the second enthalpy is the same as the theoretical value H(Th1) of the first enthalpy.
The abnormality determination unit 75 determines the abnormality in a case where the first change amount calculated by the first change amount calculation unit 72 or the second change amount calculated by the second change amount calculation unit 74 is equal to or more than a predetermined threshold value which is set in advance.
Hereinbefore, according to the composition abnormality detection unit (composition abnormality detection device) 70, the composition abnormality detection method, and the refrigeration device 1' according to the present embodiment described above, the current first and second entropies are compared with the first entropy (= second entropy) based on the composition ratio when the refrigerant is enclosed, in a case where the difference therebetween is equal to or more than the predetermined threshold value which is set in advance, the composition abnormality is determined. Accordingly, the composition abnormality is determined according to the change of the composition ratio, and thus, it is possible to detect the leakage even in a case of the slow leakage or the like such as the composition ratio being gradually changed at a relatively early stage.
In the above descriptions, the detection of the composition abnormality during the cooling operation has been described. However, during the heating operation, by installing the temperature sensor and the pressure sensor at corresponding locations, similar processing may be performed, and thus, it is possible to detect the composition abnormality similarly as in the cooling operation.
The present invention is not limited to the inventions related to the embodiments, and may be appropriately modified within a scope which does not depart from the gist.
In each embodiment, the pressure sensors 30a, 30b, and 37 and the temperature sensors 31a to 34a, 31b to 34b, and 36 are provided. However, in a case where the existing sensors provided so as to control the operation of the refrigerant circuit can be used as the sensor, it is not necessary to install a new sensor as long as various calculations are performed using the measurement values of the sensors.

Reference Signs List

1, 1':: refrigeration device
6:: outdoor heat exchanger
8:: receiver
9:: electronic expansion valve
11:: indoor heat exchanger
30a, 30b, 37:: pressure sensor
31a to 34a, 31b to 34b, 35, 36:: temperature sensor
50, 50':: controller
61:: reference value calculation unit
62:: temperature gradient calculation unit
63:: abnormality determination unit
70:: composition abnormality detection unit
71:: first enthalpy calculation unit
72:: first change amount calculation unit
73:: second enthalpy calculation unit
74:: second change amount calculation unit
75:: abnormality determination unit

Claims

A composition abnormality detection device which is applied to a refrigerant circuit using a nonazeotropic mixed refrigerant obtained by mixing a plurality kinds of refrigerants having different boiling points, the device comprising:
a plurality of temperature measurement units which are provided from a refrigerant inlet to a refrigerant outlet of a condenser;

a pressure measurement unit which measures an inlet-side pressure of the condenser;

a reference value calculation unit which calculates a reference value of a temperature gradient in the condenser using a pressure measurement value measured by the pressure measurement unit;

a temperature gradient calculation unit which calculates the temperature gradient using a plurality of temperature measurement values measured by the temperature measurement units; and

an abnormality determination unit which determines an abnormality in a case where a difference between the temperature gradient calculated by the temperature gradient calculation unit and the reference value of the temperature gradient calculated by the reference value calculation unit is outside a preset temperature range.
The composition abnormality detection device according to claim 1,
wherein in a case where an effective length of a refrigerant pipe from the refrigerant inlet to the refrigerant outlet of the condenser is defined as 100%, a start position of the effective length is defined as 0%, and an end position of the effective length is defined as 100%, the temperature measurement unit includes at least one inlet-side temperature measurement unit which is provided at the effective length of 0% and 40% and at least one outlet-side temperature measurement unit which is provided at the effective length of 90% to 100%, and
wherein the temperature gradient calculation unit calculates the temperature gradient using a temperature measurement value measured by at least one inlet-side temperature measurement unit and a temperature measurement value measured by at least one outlet-side temperature measurement unit.
The composition abnormality detection device according to claim 2,
wherein the temperature gradient calculation unit calculates, as the temperature gradient, a difference between a temperature measurement value measured by the inlet-side temperature measurement unit closest to the start position and a lowest temperature measurement value of temperature measurement values measured by other temperature measurement units.
A refrigeration device using a nonazeotropic mixed refrigerant comprising:
the composition abnormality detection device according to any one of claims 1 to 3.
A composition abnormality detection method which is applied to a refrigerant circuit using a nonazeotropic mixed refrigerant obtained by mixing a plurality kinds of refrigerants having different boiling points, the method comprising:
a step of measuring a temperature at a plurality of temperature measurement positions provided from a refrigerant inlet to a refrigerant outlet of a condenser;

a step of calculating a temperature gradient in the condenser using temperature measurement values at a plurality of measurement positions of the condenser;

a step of measuring an inlet-side pressure of the condenser;

a step of calculating a reference value of the temperature gradient from the inlet-side pressure of the condenser; and

a step of determining an abnormality in a case where a difference between the calculated temperature gradient and the reference value of the temperature gradient is outside a preset temperature range.
A composition abnormality detection device which is applied to a refrigerant circuit using a nonazeotropic mixed refrigerant obtained by mixing a plurality kinds of refrigerants having different boiling points, the device comprising:
a condenser;

an evaporator;

a receiver which is provided between the condenser and the evaporator;

a decompression unit which is provided between the receiver and the evaporator;

a first temperature measurement unit which measures a temperature of a refrigerant flowing through a portion between the condenser and the receiver;

a second temperature measurement unit which measures a temperature of a refrigerant decompressed by the decompression unit;

a pressure measurement unit which measures a pressure of the refrigerant decompressed by the decompression unit;

a first enthalpy calculation unit which calculates a first enthalpy of a cooling region from a first temperature measured by the first temperature measurement unit;

a first change amount calculation unit which calculates, as a first change amount, a change amount between a latest first enthalpy calculated by the first enthalpy calculation unit and a first enthalpy corresponding to a composition ratio of the refrigerant when the refrigerant is enclosed;

a second enthalpy calculation unit which calculates, as a second enthalpy, an enthalpy after the decompression using a second temperature measured by the second temperature measurement unit and a pressure measured by the pressure measurement unit;

a second change amount calculation unit which calculates, as a second change amount, a change amount between a latest second enthalpy calculated by the second enthalpy calculation unit and the second enthalpy corresponding to the composition ratio of the refrigerant when the refrigerant is enclosed; and

an abnormality determination unit which determines an abnormality in a case where the first change amount calculated by the first change amount calculation unit or the second change amount calculated by the second change amount calculation unit is equal to or more than a predetermined threshold value which is set in advance.