KPO-2795 DESCRIPTION
Title of Invention
REFRIGERATION APPARATUS
Technical Field
[0001]
The present invention relates to a refrigeration apparatus using a propylene-based fluorohydrocarbon or a mixture containing the propylene-based fluorohydrocarbon as refrigerant circulating in a refrigeration cycle. Background Art [0002]
A refrigerating machine oil to be used in a refrigeration apparatus, such as an air-conditioning device, has hitherto contained a substance for suppressing degradation of the refrigerating machine oil and corrosion of an expansion valve caused by an acid, such as hydrofluoric acid, to be generated through decomposition of refrigerant. For example, in Patent Literature 1 described below, there is a disclosure of a lubricating oil composition for a refrigeration apparatus in which an acid scavenger is blended in an addition amount of from 0.005 wt% to 10.0 wt% in a refrigerating machine oil. [0003]
In addition, fluorine-based refrigerants, such as R32, which is single refrigerant, and R410A and R407C, which are each mixed refrigerant, have hitherto been each used as refrigerant circulating in a refrigeration cycle of the refrigeration apparatus, such as an air-conditioning device. However, those fluorine-based refrigerants have problems of having a large impact on global warming owing to the greenhouse effect while having a small impact on destruction of the ozone layer because of being free from chlorine. In view of the foregoing, in recent years, attention has been paid to propylene-based fluorohydrocarbon refrigerant having a low global warming potential and a small impact on global warming, for example, HFO-1234yf refrigerant or HFO-1234ze(E) refrigerant. Citation List

Patent Literature [0004]
Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2011-202031 Summary of Invention Technical Problem [0005]
As compared to the other fluorine-based refrigerants, such as R32 and R410A, the propylene-based fluorohydrocarbon refrigerant has low stability, and is liable to be decomposed when the refrigerant is exposed to a high-temperature environment or air and water are mixed therein, and also the amount of an acid, such as hydrofluoric acid, to be generated through its decomposition is large. The acid to be generated through the decomposition of the refrigerant has a risk of causing degradation of the refrigerating machine oil to be used in the refrigeration apparatus and corrosion of a component, such as an expansion valve. In addition, there is a risk in that the degraded refrigerating machine oil and sliding wear powder in a compressor constituting the air-conditioning device bind to each other to form sludge, to thereby cause clogging in the component of the refrigerant circuit, such as the expansion valve. In addition, when an acid scavenger is added in an amount of 10 wt% based on the lubricating oil composition for a refrigeration apparatus disclosed in Patent Literature 1, abnormal generation of the sludge cannot be suppressed while generation of fluorine can be suppressed. [0006]
In addition, as compared to the other fluorine-based refrigerants, the propylene-based fluorohydrocarbon refrigerant has good compatibility with the refrigerating machine oil. When a refrigerating machine oil in which the refrigerant is dissolved and which is reduced in viscosity is supplied to a sliding part of the compressor, the sliding part of the compressor is subjected to metal contact to cause abnormal heat, and thus generation of the acid owing to the decomposition of the refrigerant is promoted.

[0007]
The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a refrigeration apparatus which is suppressed in degradation of a refrigerating machine oil, corrosion of an expansion valve, and abnormal generation of sludge, and has high reliability. Solution to Problem [0008]
According to one embodiment of the present invention, there is provided a refrigeration apparatus, including a refrigerant circuit configured to circulate refrigerant by connecting a compressor, a condenser, an expansion mechanism, and an evaporator through a refrigerant pipe, wherein the refrigerant contains at least 10 wt% or more of HFO-based refrigerant and at least 50 wt% or more of HFC-based refrigerant, and wherein a refrigerating machine oil for lubricating a sliding part of the compressor has blended therein an acid scavenger in an addition amount of from 0.1 wt% to 1.0 wt%.
Advantageous Effects of Invention [0009]
The refrigeration apparatus according to the embodiment of the present invention has a configuration in which a propylene-based fluorohydrocarbon or a mixture containing the propylene-based fluorohydrocarbon is used as the refrigerant, and the refrigerating machine oil sealed in a compression element has blended therein the acid scavenger in an amount effective for scavenging an acid, such as hydrofluoric acid, to be generated through decomposition of the refrigerant. Thus, the degradation of the refrigerating machine oil, the corrosion of an expansion valve, and the abnormal generation of sludge can be suppressed. Brief Description of Drawings [0010]
[Fig. 1] Fig. 1 is a schematic view for schematically illustrating a refrigerant circuit of a refrigeration apparatus according to an embodiment of the present invention.

Description of Embodiments
[0011]
Embodiment
The configuration and operation of a refrigeration apparatus according to the present invention are described below based on an illustrated embodiment. Fig. 1 is a schematic view for schematically illustrating a refrigerant circuit of a refrigeration apparatus according to an embodiment of the present invention. As illustrated in Fig. 1, a refrigeration apparatus 1 of this embodiment includes a refrigerant circuit configured to circulate refrigerant by sequentially connecting a compressor 2, a four-way switching valve 3, an outdoor heat exchanger 4, an expansion mechanism 5, and an indoor heat exchanger 6 through a refrigerant pipe, and is used for indoor cooling and heating by performing a vapor compression-type refrigeration cycle operation. [0012]
The compressor 2 is configured to compress the refrigerant suctioned therein and eject the refrigerant in a high-temperature and high-pressure state. A refrigerant ejection side thereof is connected to the four-way switching valve 3, and a refrigerant suction side thereof is connected to an accumulator 9. For example, the compressor 2 has a configuration in which an operation capacity (frequency) is variable. For example, a displacement-type compressor to be driven by a motor controlled by an inverter (illustration of those components is omitted) is used as the compressor 2. [0013]
The four-way switching valve 3 has a refrigerant passage switching function. At the time of cooling operation, as indicated by the arrow of a solid line of Fig. 1, the four-way switching valve 3 switches a refrigerant passage so that the refrigerant ejection side of the compressor 2 and a gas side of the outdoor heat exchanger 4 are connected to each other, and the refrigerant suction side of the compressor 2 and a gas side of the indoor heat exchanger 6 are connected to each other. Meanwhile, at the time of heating operation, as indicated by the arrow of a broken line of Fig. 1, the four-way switching valve 3 switches the refrigerant passage so that the refrigerant ejection side of the compressor 2 and the gas side of the indoor heat exchanger 6 are

connected to each other, and the refrigerant suction side of the compressor 2 and the
gas side of the outdoor heat exchanger 4 are connected to each other.
[0014]
The outdoor heat exchanger 4 functions as a condenser at the time of cooling operation, and is configured to perform heat exchange between the refrigerant ejected from the compressor 2 and air. In addition, the outdoor heat exchanger 4 functions as an evaporator at the time of heating operation, and is configured to perform heat exchange between the refrigerant having flowed from the expansion mechanism 5 and air. The outdoor heat exchanger 4 is configured to suction outdoor air with an outdoor air-sending device 7, and discharge air having been subjected to the heat exchange with the refrigerant outdoors. The gas side of the outdoor heat exchanger 4 is connected to the four-way switching valve 3, and a liquid side of the outdoor heat exchanger 4 is connected to the expansion mechanism 5. [0015]
The expansion mechanism 5 is configured to reduce the pressure of the refrigerant flowing in the refrigerant circuit to expand the refrigerant, and an example thereof is an electronic expansion valve in which its opening degree is variably controlled. One side of the expansion mechanism 5 is connected to the outdoor heat exchanger 4, and the other side of the expansion mechanism 5 is connected to the indoor heat exchanger 6. [0016]
The indoor heat exchanger 6 functions as an evaporator at the time of cooling operation, and is configured to perform heat exchange between the refrigerant having flowed from the expansion mechanism 5 and air. In addition, the indoor heat exchanger 6 functions as a condenser at the time of heating operation, and is configured to perform heat exchange between the refrigerant ejected from the compressor 2 and air. The indoor heat exchanger 6 is configured to suction indoor air with an indoor air-sending device 8, and supply air having been subjected to the heat exchange with the refrigerant indoors. The gas side of the indoor heat

exchanger 6 is connected to the four-way switching valve 3, and a liquid side of the
outdoor heat exchanger 6 is connected to the expansion mechanism 5.
[0017]
Next, the operation of the refrigeration apparatus 1 at the time of cooling operation is described.
The compressor 2 compresses low-pressure gas refrigerant, and ejects high-temperature and high-pressure gas refrigerant. The refrigerant ejected from the compressor 2 passes through the four-way switching valve 3, and is supplied to the outdoor heat exchanger 4. When passing through the outdoor heat exchanger 4, the high-temperature and high-pressure gas refrigerant is condensed and turns into high-pressure liquid refrigerant. The liquid refrigerant having passed through the outdoor heat exchanger 4 passes through an expansion valve serving as the expansion mechanism 5 to turn into low-pressure gas-liquid mixed refrigerant, and the low-pressure gas-liquid mixed refrigerant is supplied to the indoor heat exchanger 6. When passing through the indoor heat exchanger 6, the refrigerant in a low-pressure gas-liquid mixed state turns into low-temperature and low-pressure gas refrigerant. The refrigerant having passed through the indoor heat exchanger 6 is supplied to the compressor 2. [0018]
At the time of cooling operation, the outdoor heat exchanger 4 functions as a condenser, and the indoor heat exchanger 6 functions as an evaporator. That is, the room is cooled by evaporation latent heat of the refrigerant to be generated in the indoor heat exchanger 6. Meanwhile, at the time of heating operation, the outdoor heat exchanger 4 functions as the evaporator, and the indoor heat exchanger 6 functions as the condenser by switching the four-way switching valve 3. That is, the room is heated by condensation latent heat of the refrigerant to be generated in the outdoor heat exchanger 4. [0019]
In this embodiment, HFO-based refrigerant, which is propylene-based fluorohydrocarbon refrigerant, is used as the refrigerant circulating in the refrigerant

circuit of the refrigeration apparatus 1. Specifically, the HFO-based refrigerant is used as HFO alone or as mixed refrigerant further containing R32. The mixed refrigerant containing the HFO-based refrigerant is mixed refrigerant containing at least 10 wt% or more of the HFO refrigerant and at least 50 wt% or more of the R32 refrigerant, which is HFC refrigerant. Preferred examples of the HFO refrigerant include HFO-1234yf and HFO-1234ze(E). In addition, the mixed refrigerant has a global warming potential of preferably 1,000 or less, more preferably 500 or less. [0020]
The HFO-based refrigerant has less impact on global warming as compared to other fluorine-based refrigerants, such as R32, which is single refrigerant, and R410A and R407C, which are each mixed refrigerant. However, the HFO-based refrigerant has low stability, and hence the amount of an acid, such as hydrogen fluoride (hydrofluoric acid), formic acid, or acetic acid, to be generated through its decomposition is large. The acid to be generated through the decomposition of the refrigerant is dissolved in water contained in the refrigerant and a refrigerating machine oil to circulate in the refrigerant circuit, to thereby cause degradation of the refrigerating machine oil. Further, when the acid adheres to the expansion valve serving as the expansion mechanism 5, a metal component of the expansion valve corrodes to cause a failure in the expansion mechanism 5. In addition, there is a risk in that the refrigerating machine oil degraded with the acid and sliding wear powder in the compressor 2 bind to each other to form sludge, to thereby cause clogging in a component of the refrigerant circuit, such as the expansion valve. [0021]
Next, examples of operation modes of the refrigeration apparatus 1 in which the HFO refrigerant is liable to be decomposed are given. In an operation in which the high-pressure gas refrigerant to be ejected from the compressor 2 has a temperature of, for example, more than 120 degrees Celsius, the temperature of a sliding part of the compressor 2 may be locally increased, and there is a risk in that the HFO refrigerant is thermally decomposed. In addition, when a large amount of the liquid refrigerant is returned to the compressor 2 at the time of activation of the

refrigeration apparatus 1, an operation is performed under a state in which the liquid refrigerant is dissolved in the refrigerating machine oil in the compressor 2, and the refrigerating machine oil reduced in viscosity is supplied to the sliding part of the compressor 2. In this operation, there is a risk in that the sliding part of the compressor 2 is subjected to metal contact to cause abnormal heat, and thus the HFO refrigerant is thermally decomposed. [0022]
In view of the foregoing, the refrigerating machine oil to be used in the refrigeration apparatus 1 of this embodiment has blended therein an acid scavenger in an amount of from 0.1 wt% to 1.0 wt%. The refrigerating machine oil is a lubricating oil to be used for preventing wear and seizure of the sliding part of the compressor 2. When the compressor 2 is a rotary compressor, the sliding part of the compressor 2 corresponds to, for example, a sliding surface between a vane and a roller or a sliding surface between a crankshaft and a bearing. The acid scavenger is an additive to be used for scavenging the acid, such as hydrofluoric acid, to be generated through the decomposition of the HFO-based refrigerant. [0023]
Next, the composition of the refrigerating machine oil to be used in this embodiment is described. The refrigerating machine oil is formed mainly of a base oil, an acid scavenger, an extreme pressure agent, and an antioxidant. [0024]
A mineral oil or a synthetic oil is used as the base oil. The base oil is appropriately selected so as to provide a refrigerating machine oil which has a viscosity enough to enable fluid lubrication in the sliding part of the compressor 2 while having good compatibility with the HFO-based refrigerant to be used in the refrigeration apparatus 1. Examples of the mineral oil include a naphthene-based mineral oil and a paraffin-based mineral oil. Examples of the synthetic oil include a polyvinyl ether, a polyol ester, a polyalkylene glycol, and an alkylbenzene. In this embodiment, the synthetic oil, such as the polyvinyl ether or the polyol ester, is

preferably used as the base oil. As the base oil, the above-mentioned mineral oils
and synthetic oils may be used in combination as a mixture.
[0025]
The acid scavenger is an additive to be used for suppressing the degradation of the refrigerating machine oil caused by the acid, such as hydrofluoric acid, to be generated through the decomposition of the HFO-based refrigerant through a reaction with the acid. The acid scavenger is contained in an amount of from 0.1 wt% to 1.0 wt% in the refrigerating machine oil. Examples of the acid scavenger include an epoxy compound, a carbodiimide compound, and a terpene-based compound. [0026]
The extreme pressure agent is an additive to be used for preventing wear and seizure of the sliding part of the compressor 2 or other units. The refrigerating machine oil forms an oil film between surfaces of members sliding with respect to each other in the sliding part to prevent contact between these sliding members. However, when the refrigerating machine oil contains a base oil having a low viscosity, or is reduced in viscosity when a large amount of the refrigerant is dissolved therein, or when high pressure is applied onto the sliding members, the sliding members are liable to be subjected to metal contact. Even in such case, the extreme pressure agent suppresses the occurrence of wear and seizure of the sliding part by forming the film through reactions with the surfaces of the members sliding with respect to each other. Examples of the extreme pressure agent include a phosphoric acid ester, a phosphorous acid ester, a thiophosphoric acid salt, and a sulfurized ester, and specific examples thereof include tricresyl phosphate (TCP), triphenyl phosphate (TPP), and triphenyl phosphorothioate (TPPT). [0027]
The antioxidant is an additive to be used for preventing oxidation of the refrigerating machine oil. Specific examples of the antioxidant include zinc dithiophosphate, organic sulfur compounds, phenol-based antioxidants, such as 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, and 2,2ʹ-methylenebis(4-methyl-6-tert-butylphenol), amine-based antioxidants, such as phenyl-α-

naphthylamine and N,Nʹ-di-phenyl-p-phenylenediamine, and N,Nʹ-disalicylidene-1,2-diaminopropane. [0028]
Next, an influence of the refrigerating machine oil to be used in the refrigeration apparatus of this embodiment on the refrigeration apparatus 1 is described based on Table 1 below. The applicant performed a product pilot test, and analyzed the influence of the refrigerating machine oil on the refrigeration apparatus 1. [0029]
The test conditions of the product pilot test were as follows: the temperature of a refrigerant gas to be ejected from the compressor 2 was 140 degrees Celsius; the operation time period of the refrigeration apparatus 1 was 500 hours; and the operation pressure of the refrigeration apparatus 1 was a value appropriately set. A polyvinyl ether oil was used as a base oil of the refrigerating machine oil. An acid scavenger was blended in the refrigerating machine oil in various addition amounts of 0.005 wt%, 0.05 wt%, 0.1 wt%, 1.0 wt%, 6.0 wt%, and 10.0 wt%. The refrigeration apparatus 1 was driven, and the state of the expansion valve serving as the expansion mechanism 5 of the refrigeration apparatus 1 was confirmed. Specifically, the expansion valve after the test was subjected to elemental analysis with an X-ray apparatus, and the amount of fluorine serving as a refrigerant decomposition product and the amount of sludge adhering to the expansion valve were determined. The test results of the product pilot test are shown in Table 1.

[0031]
As criteria for determining whether the refrigerating machine oil passes or fails the test, evaluation results of R410A refrigerant were used as a reference. A case of having a fluorine detection amount of 5 wt% or less and a sludge generation amount of 1 wt% or less was determined as "Pass" and other cases were determined as "Fail". [0032]
In Table 1, each of the cases "I" and "II", in which the addition amount of the acid scavenger was from 0.005 wt% to 0.05 wt%, was determined as "Fail" because the fluorine detection amount was more than 5 wt%, and the corrosion of the expansion valve was observed. In addition, each of the cases "V" and "VI", in which the addition amount of the acid scavenger was from 6 wt% to 10 wt%, was determined as "Fail" because the sludge generation amount was 1 wt% or more, and the generation of a large amount of sludge was observed. Meanwhile, each of the cases "III" and "IV", in which the addition amount of the acid scavenger was from 0.1 wt% to 1.0 wt%, was determined as "Pass" because both the fluorine detection amount and the sludge generation amount were acceptable. [0033]

From Table 1, it was revealed that, in the refrigeration apparatus using the HFO-based refrigerant, the corrosion of the expansion valve and the abnormal generation of the sludge were suppressed when the addition amount of the acid scavenger in the refrigerating machine oil was from 0.1 wt% to 1.0 wt%. [0034]
Further, it was able to be confirmed that the fluorine detection amount was significantly reduced and an effect of suppressing the corrosion of the expansion valve was improved when the addition amount of the acid scavenger was from 0.2 wt% to 1.0 wt%. [0035]
Accordingly, in the refrigeration apparatus 1 of this embodiment, the acid, such as hydrofluoric acid, to be generated through the decomposition of the HFO-based refrigerant is scavenged by the acid scavenger contained in an amount of from 0.1 wt% to 1.0 wt%, more preferably from 0.2 wt% to 1.0 wt% in the refrigerating machine oil. With this, the degradation of the refrigerating machine oil, the corrosion of the expansion valve serving as the expansion mechanism 5, and the abnormal generation of the sludge caused by the acid to be generated through the decomposition of the HFO-based refrigerant are suppressed. Accordingly, the reliability of the refrigeration apparatus 1 can be improved. [0036]
The present invention has been described based on the embodiment, but the present invention is not limited to the configuration of the embodiment described above. For example, the contents of the configuration of the refrigerant passage (pipe connection), the configuration of an element of the refrigerant circuit, such as the compressor 2, the four-way switching valve 3, the outdoor heat exchanger 4, the expansion mechanism 5, or the indoor heat exchanger 6, and other configurations are not limited to the contents described in the embodiment, and may appropriately be changed within the scope of the technology of the present invention. In a word, just to make sure, it is noted that various changes, applications, and utilization ranges

adopted by a so-called person skilled in the art as required are also included in the gist (technical scope) of the present invention. Reference Signs List [0037]
1 refrigeration apparatus 2 compressor 3 four-way switching
valve 4 outdoor heat exchanger 5 expansion mechanism 6 indoor heat
exchanger 7 outdoor air-sending device 8 indoor air-sending device 9
accumulator

CLAIMS [Claim 1]
A refrigeration apparatus, comprising a refrigerant circuit configured to circulate refrigerant by connecting a compressor, a condenser, an expansion mechanism, and an evaporator through a refrigerant pipe,
wherein the refrigerant contains at least 10 wt% or more of HFO-based refrigerant and at least 50 wt% or more of HFC-based refrigerant, and
wherein a refrigerating machine oil for lubricating a sliding part of the compressor contains therein an acid scavenger in an addition amount of from 0.1 wt% to 1.0 wt%. [Claim 2]
The refrigeration apparatus of claim 1, wherein the addition amount of the acid scavenger is 0.2 wt% or more. [Claim 3]
The refrigeration apparatus of claim 1 or 2, wherein the refrigerating machine oil further contains therein an extreme pressure agent. [Claim 4]
The refrigeration apparatus of any one of claims 1 to 3, wherein the refrigerating machine oil further contains therein an antioxidant. [Claim 5]
The refrigeration apparatus of any one of claims 1 to 4, wherein the refrigerating machine oil contains a polyvinyl ether oil. [Claim 6]
The refrigeration apparatus of any one of claims 1 to 4, wherein the refrigerating machine oil contains a polyol ester oil. [Claim 7]
The refrigeration apparatus of any one of claims 1 to 4, wherein the refrigerating machine oil contains an alkylbenzene oil. [Claim 8]

The refrigeration apparatus of any one of claims 1 to 7, wherein the HFO-based refrigerant includes at least one of HFO-1234yf or HFO-1234ze(E). [Claim 9]
The refrigeration apparatus of any one of claims 1 to 8, wherein the HFC-based refrigerant is R32. [Claim 10]
The refrigeration apparatus of any one of claims 1 to 9, wherein the refrigerant has a global warming potential of 1,000 or less.