JPH0841448A - Freezing cycle using hfc-based non-azeotropic cooling medium mixture and freezing apparatus - Google Patents

Abstract

PURPOSE:To provide the freezing cycle using HFC-based non-azeotropic cooling medium mixture as a cooling medium and a specific oil which is poorly compatible with the mixture, free from hazard of depletion of ozone layer and non-inflammable as a freezer oil, and capable of performing a stable operation for a long period of time. CONSTITUTION:This freezing cycle uses HFC-based non-azeotropic cooling medium mixture (e.g. a mixture of difluoromethane/pentafluoroethane/1,1,1,2- tetrafluoroethane of 20/40/40 in terms of weight ratio) as a cooling medium and an oil (e.g. a mineral oil or an alkylbenzenebased oil) which is poorly compatible with the mixture and separates into more than three layers when mixed with the mixture, as a freezer oil. Further, in the case where a rotary compressor is used as a compressor, an alkylbenzene-based oil is preferably used as the freezer oil because of good return to the compressor, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating cycle and a refrigerating apparatus using an HFC-based non-azeotropic refrigerant mixture, and more specifically, it is nonflammable and compatible with no danger of destroying the ozone layer. The present invention relates to a refrigerating cycle and a refrigerating apparatus using an HFC-based non-azeotropic refrigerant mixture that can be stably operated for a long period of time even if a refrigerating machine oil such as a poorly-refined mineral oil or an alkylbenzene-based oil is used.

[0002]

2. Description of the Related Art Conventionally, refrigerants used in refrigerators are dichlorodifluoromethane (hereinafter referred to as R-12) and azeotropic mixed refrigerants R-12 and 1,1-difluoroethane (hereinafter referred to as R-152a). R-500 consisting of
There are many. The boiling point of R-12 is -29.65 ° C at atmospheric pressure,
The boiling point of R500 is −33.45 ° C., which is suitable for a normal refrigerating apparatus, and a refrigerating cycle using a refrigerating machine oil such as a mineral oil or an alkylbenzene-based oil compatible with a CFC-based refrigerant such as R-12 is It has a history of about 30 years, and efforts have been made to improve it, leading to high quality levels such as reliability and durability.

However, due to their high ozone depletion potential, each of the above refrigerants destroys the ozone layer when it reaches the ozone layer above the earth by being released into the atmosphere.
The destruction of the ozone layer is caused by chlorine groups (Cl) in the refrigerant. Therefore, a refrigerant having a low chlorine group content, for example, chlorodifluoromethane (HCFC-22,
R-22), chlorine-free refrigerants such as difluoromethane (HFC-32, hereinafter R-32), pentafluoroethane (HFC-125, hereinafter R)
-125) and 1,1,1,2-tetrafluoroethane (HFC-134a, hereinafter referred to as R-134a) are considered as alternative refrigerants for these. This R-22
Has a boiling point of −40.82 ° C. at atmospheric pressure, R-32 has a boiling point of −51.7 ° C., and R-125 has a boiling point of −48.5.
The boiling point of R-134a is -26.0 ° C.

It has been considered that one of the important factors is that the refrigerating machine oil used for these HFC-based refrigerants is first compatible with the HFC-based refrigerant.
Since mineral oils and alkylbenzene-based oils have poor compatibility, it has been considered that refrigeration cycles and refrigeration systems that use both in combination cannot operate stably over a long period of time.

However, a refrigerating cycle using an ester type lubricating oil, an ether type lubricating oil or a mixed lubricating oil thereof as a refrigerating machine oil having a high compatibility with an HFC type refrigerant is a conventional CF.
Compared to a refrigeration cycle using C or HCFC refrigerant (designated CFC), there is a large tendency that the lubricity and electrical characteristics are deteriorated, which is a problem.

There are various possible causes for this, but ester-based lubricating oil and the like used in combination with HFC-based refrigerants are not sufficiently effective as extreme pressure agents, resulting in friction and wear of sliding parts inside the compressor. The temperature tends to rise, sludge components (dust) are likely to be generated due to abrasion, and moisture tends to be absorbed or hydrolyzed. Low hygroscopicity and hydrolyzability, good electrical characteristics, high lubricity, and economical
A lubricating oil that can be used as a mixture with an FC-based refrigerant has not been obtained yet.

A refrigeration system using HFC134a as an HFC refrigerant and an incompatible hard alkylbenzene oil as a refrigerating machine oil has been proposed (JP-A-5-157379), but it is separated from HFC134a in a header in a refrigeration circuit. In order to efficiently return the hard alkylbenzene oil to the compressor, it is necessary to change the refrigerant flow from the upper side to the lower side of the header and insert a suction pipe for sucking the hard alkylbenzene oil into the header. there were.

[0008]

The object of the present invention is to provide HF
Ester-based lubricating oil or the like as a refrigerating machine oil having a good compatibility with the C-based refrigerant tends to absorb moisture or hydrolyze,
Do not use because there is a problem with lubricity and electrical characteristics.
Although it has poor compatibility with C-based refrigerants but does not have hygroscopicity or hydrolyzability, it uses mineral oil or alkylbenzene-based oil with good electrical characteristics as refrigerating machine oil, without changing the conventional refrigeration cycle or refrigeration equipment. Moreover, it is an object of the present invention to provide a refrigeration cycle and a refrigeration system using an HFC refrigerant that can be stably and efficiently operated for a long period of time.

[0009]

As a result of intensive studies in view of the above problems, the present inventor has found that the above problems can be solved by using an HFC-based non-azeotropic refrigerant mixture, and has completed the present invention.

According to the first aspect of the present invention, H is used as the refrigerant.
In a refrigeration cycle using an FC-based non-azeotropic refrigerant mixture, the refrigerant mixture and the oil have poor compatibility, and an oil that separates into three or more layers even when the two are mixed is used as a refrigerator oil It is a refrigeration cycle using an HFC-based non-azeotropic refrigerant mixture.

A second aspect of the present invention is the refrigeration cycle using the HFC-based non-azeotropic refrigerant mixture according to the first aspect, wherein the refrigerating machine oil is an oil selected from mineral oil and alkylbenzene type oil.

According to a third aspect of the present invention, a rotary compressor is used as a compressor and an alkylbenzene type oil is used as a refrigerating machine oil. The HFC type non-azeotropic refrigerant mixture according to the first aspect is used. It is a refrigeration cycle.

According to a fourth aspect of the present invention, a refrigerating apparatus is provided with a condenser for condensing and liquefying a refrigerant, an evaporator for evaporating a liquefied refrigerant, and a compressor for compressing the evaporated and vaporized refrigerant and discharging it to the condenser. In the above, an HFC-based non-azeotropic refrigerant mixture is used as the refrigerant to be compressed by the compressor, and as the refrigerating machine oil, the refrigerant mixture and the oil have poor compatibility, and an oil that separates into three layers or more even if both are mixed is used. It is a refrigerating device characterized by being used.

A fifth aspect of the present invention is the refrigerating apparatus according to the fourth aspect, wherein the refrigerating machine oil is an oil selected from mineral oil and alkylbenzene oil.

The invention according to claim 6 of the present invention is the refrigerating apparatus according to claim 4, wherein a rotary compressor is used as the compressor and an alkylbenzene oil is used as the refrigerating machine oil.

[0016]

[Function] HFC-based refrigerants and mineral oils and alkylbenzene-based oils have poor compatibility, so it was thought that they could not be used in combination, but HFC-based non-azeotropic refrigerant mixtures were used as HFC-based refrigerants. For example, without changing the conventional refrigeration cycle or refrigeration equipment, mineral oil or alkylbenzene oil can be used without problems such as moisture absorption, hydrolysis, lubricity and electrical characteristics, and moreover, it is discharged from the compressor to the refrigerant circuit. Since mineral oil, alkylbenzene oil, etc. can be collected in the compressor and no sludge is generated, stable and efficient operation can be achieved over a long period of time.

CF is used because no ester type lubricating oil is used.
The water content can be controlled to the same extent as in the refrigeration cycle using a C-based refrigerant, and mineral oil, alkylbenzene-based oil, etc. have excellent electrical insulation and moisture absorption resistance, and can be returned to the compressor well. There is no risk of fire if the refrigerant should leak.

A test using HFC type refrigerant and alkylbenzene type oil was conducted using the refrigeration cycle shown in FIG. 1 in which sight glasses 17 to 22 were provided in various places of the refrigeration cycle so that the states of the refrigerant and the lubricating oil could be observed. As a result, it was observed that when starting from the refrigerant stagnation state, the lubricating oil 6a in the compressor 1 foams for several minutes, but thereafter, the foaming disappears stably and the lubricating oil returns to the compressor 1 in a short time. Was done. When the refrigerant composition of the refrigerant mixture in the discharge part of the compressor 1, the outlet part of the condenser 2 and the suction part of the compressor 1 is analyzed, it shows almost the same refrigerant composition ratio as the charged refrigerant mixture, and shows stable and efficient operation. It proved that he could drive well.

1 is a compressor, 2 is a condenser, 3 is a capillary tube, 4 is an evaporator, 5 is a header, 6 is lubricating oil (6a is alkylbenzene oil, 6b is ester oil), 11 is a closed container, 12 is an electric motor, 13 is an insulating coated electric wire, 14 is a cylinder, and 15 is a bearing. From this test result, if the HFC-based non-azeotropic refrigerant mixture is used as the HFC-based refrigerant, and the oil that separates into three layers or more even when both are mixed is used as the refrigerating machine oil, the refrigerating machine oil becomes H
It can be seen that even in the case of an alkylbenzene oil having a low compatibility with an FC refrigerant, short-time foaming has no practical problem, and the alkylbenzene oil discharged from the compressor to the refrigerant circuit can be recovered by the compressor.

The HFC-based non-azeotropic refrigerant mixture used in the present invention is a mixture of two or more HFC-based refrigerants, and the boiling point and dew point of the mixture are different from each other. For example, R125 / R143a / 134
a (weight ratio 44/52/4) (R404A, boiling point -4
6.78 ° C, dew point -46.08 ° C, trade name: HP62,
Made by DuPont, hereinafter referred to as HP62), R32 / R12
5 / 134a (weight ratio 20/40/40) (R407
A, boiling point -45.4 ° C, dew point -38.8 ° C, trade name: K
LEA60G2, manufactured by ICI, hereinafter referred to as KLEA60) and the like.

The refrigerating machine oil used in the present invention has poor compatibility with the HFC-based non-azeotropic refrigerant mixture, and when both are mechanically mixed and left to stand, they are separated into three layers or more. In many cases, the upper layer is mainly composed of frozen oil, the middle layer is a mixed layer of frozen oil and refrigerant, and the lower layer is mainly composed of refrigerant, but the concentration of frozen oil is small on the layer mainly composed of refrigerant. Since there is a case where a mixed layer with a refrigerant having a gradient that greatly changes from the above is formed, in the present invention, such an oil is also referred to as "when the refrigerant mixture and the oil are not compatible and both are mixed. It shall be included in the category of "refrigerating machine oil that separates into three or more layers".

In the present invention, the reason why the alkylbenzene oil discharged from the compressor to the refrigerant circuit can be recovered in the compressor is not clear, but one of the reasons is that the HFC nonazeotropic refrigerant mixture is used in the refrigeration cycle. As described above, it is conceivable to form a mixed layer of the frozen oil and the refrigerant or a mixed layer of the refrigerant having a gradient such that the concentration of the frozen oil changes from small to large. Further, since the refrigerant used in the present invention is a non-azeotropic mixture, the refrigerant component having a high boiling point is delayed in evaporation in the evaporator or the like in the refrigeration circuit, and the refrigerant component still in a liquid state returns the alkylbenzene oil to the compressor. It is also possible that it worked. However, as a matter of course, the reason why the alkylbenzene-based oil or the like discharged from the compressor to the refrigerant circuit in the present invention can be collected in the compressor is not limited to these reasons.

The combination of the type of compressor such as a rotary compressor or reciprocating compressor and the type of refrigerating machine oil such as mineral oil or alkylbenzene is not particularly limited. However, when a rotary compressor is used as the compressor, it is preferable to use an alkylbenzene-based oil as the refrigerating machine oil because the oil can be easily returned to the compressor.

[0024]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples without departing from the gist of the present invention.

Example 1 A mixed refrigerant having the non-azeotropic refrigerant composition, boiling point and dew point shown in Table 1 (R-290 in Table 1)
Is propane) and the alkylbenzene oil (trade name: CF32, manufactured by Idemitsu Petroleum Co., Ltd.) is used as a lubricating oil. The symbols in Table 1 indicate the compatibility between the lubricating oil and the mixed refrigerant, and ○ indicates good compatibility. X indicates that the compatibility is poor.), And the freezer and compressor of the model shown in Table 2 are used, and the lubricating oil filling amount (230 ml) and the mixed refrigerant enclosed amount (270 to 320 g) are used for 10 hours. After the operation, the alkylbenzene-based oil discharged from the compressor into the refrigerant circuit is discharged from the compressor starting from the start of sleeping observed in the sight glass (22) of the compressor suction section (g). I measured the time (minutes) before returning to.

The results are shown in Table 3.

(Examples 2 to 5) Tests were conducted under the conditions shown in Table 3 in the same manner as in Example 1, and the results are also shown in Table 3.

(Comparative Examples 1 and 2) Tests were conducted under the conditions shown in Table 3 in the same manner as in Example 1 except that a non-azeotropic mixed refrigerant (HP80) having a good compatibility with the lubricating oil CF32 was used, and the results are shown. Are also shown in Table 3.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

From the results shown in Table 3, the non-azeotropic mixed refrigerants having a good compatibility with the lubricating oil CF32 are better in Examples 1 to 5 using the non-azeotropic mixed refrigerant having a poor compatibility with the lubricating oil CF32. It can be seen that the lubricating oil returns to the compressor earlier than in the cases of Comparative Examples 1 and 2 in which No. (Examples 6 to 8)

A check valve 16 is attached to the suction portion of the compressor 1 at the position shown in FIG. 2, and the check valve 16 is opened under the conditions shown in Table 4 in the same manner as in the first embodiment. The test was conducted in the same manner as in Example 1 except that the check valve 16 was closed after running for a period of time and then the reduction amount of the lubricating oil was measured. The results are shown in Table 4.

(Comparative Example 3) A test was conducted under the conditions shown in Table 4 in the same manner as in Example 6 except that a non-azeotropic mixed refrigerant (HP80) having a good compatibility with the lubricating oil CF32 was used, and the results were combined. Are shown in Table 4.

(Comparative Examples 4 to 5) Tests were conducted under the conditions shown in Table 4 in the same manner as in Example 6 except that the check valve 16 was left open without being closed. Shown in FIG.

[0036]

[Table 4]

From the results shown in Table 4, an example in which the check valve 16 was operated for 10 hours with the check valve 16 opened and then the check valve 16 was closed and the reduction amount of the lubricating oil was measured 6 ~
In the case of 8, the reduction amount of the lubricating oil of the compressor is small. By closing the check valve 16 after operating for 10 hours, it was possible to prevent the refrigerant from flowing from the high pressure side to the low pressure side of the compressor to move the lubricating oil from the compressor to other parts of the refrigeration circuit. I understand.
Even in the case of Examples 6 to 8 using the non-azeotropic mixed refrigerant having poor compatibility with the lubricating oil CF32, the lubricating oil CF3 is also used.
It can be seen that the lubricating oil returns to the compressor as in the case of using the non-azeotropic mixed refrigerant having good compatibility with 2 (Comparative Example 3).

Example 9 The non-azeotropic refrigerant composition (KLEA60) shown in Table 1 was used, the alkylbenzene oil (CF32) was used as the lubricating oil, and the freezer and compressor of the model shown in Table 2 were used. After operating for 20 hours under the conditions of the lubricating oil filling amount (230 ml) and the mixed refrigerant filling amount (300 g) (room temperature 25.1 ° C./compressor discharge temperature 79.9).
(° C / compressor suction temperature 29.8 ° C), the refrigerant composition of the refrigerant mixture in the discharge part of the compressor 1, the outlet part of the condenser 2 and the suction part of the compressor 1 was analyzed.

The results are shown in Table 5.

(Comparative Example 6) The same operation as in Example 9 was carried out for 20 hours except that the ester type lubricating oil shown in Table 2 (trade name: α32S, manufactured by Japan Energy Company, manufactured by Idemitsu Oil Company) was used as the lubricating oil. (Greenhouse 21.8 ° C./compressor discharge temperature 71.3 ° C./compressor suction temperature 23.
At 7 ° C.), the refrigerant composition of the refrigerant mixture in the discharge part of the compressor 1, the outlet part of the condenser 2 and the suction part of the compressor 1 was analyzed.

The results are shown together in Table 5.

[0042]

[Table 5]

From the results shown in Table 5, the composition of the non-azeotropic refrigerant (KLE
In the case of Comparative Example 6 in which the ester-based lubricating oil α32S having good compatibility with A60) was used, the refrigerant composition of the refrigerant mixture in each part was slightly different from the refrigerant composition ratio of the charged refrigerant mixture, but operated stably and efficiently. We were able to. On the other hand, the refrigerant composition of the refrigerant mixture of each part in Example 9 was almost the same as the refrigerant composition ratio of the charged refrigerant mixture, and it can be seen that the operation was more stable and efficient than that of Comparative Example 6.

[0044]

INDUSTRIAL APPLICABILITY As described above, the present invention relates to a refrigeration cycle and a refrigerating apparatus using an HFC-based non-azeotropic refrigerant mixture, and since the HFC-based non-azeotropic refrigerant mixture is used, there is a risk of destroying the ozone layer. However, it is possible to stably operate for a long period of time by using a refrigerating machine oil such as a mineral oil or an alkylbenzene oil that is nonflammable and has poor compatibility.

Since the HFC-based non-azeotropic refrigerant mixture is used as the HFC-based refrigerant and the mineral oil or the alkylbenzene-based oil is used as the refrigerating machine oil, it does not absorb or hydrolyze,
Since there is no problem of deterioration of lubricity and electrical characteristics, and refrigeration oil discharged from the compressor to the refrigerant circuit can be collected in the compressor without changing the conventional refrigeration cycle or refrigeration system, and no sludge is generated. It is possible to operate stably and efficiently for a long period of time.

Since the refrigerating cycle and the refrigerating apparatus of the present invention do not use an ester type lubricating oil or the like, it is possible to manage the water content to the same degree as that of the refrigerating cycle and the refrigerating apparatus using a CFC type refrigerant, and to improve the electric insulation and Excellent hygroscopicity, good return of lubricating oil, and no risk of fire even if the refrigerant should leak. It is easy to maintain and economical, so it has high industrial utility value.

[Brief description of drawings]

FIG. 1 is a refrigeration circuit diagram used in the present invention.

FIG. 2 is another refrigeration circuit diagram used in the present invention.

[Explanation of symbols]

 1 Compressor 2 Condenser 3 Capillary tube 4 Evaporator 5 Header 6 Lubricating oil 6a Alkylbenzene oil 6b Ester oil 11 Closed container 12 Electric motor 13 Insulated electric wire 14 Cylinder 15 Bearing 16 Check valve 19-24 Sight glass

Claims (6)

[Claims] 1. In a refrigeration cycle using a HFC-based non-azeotropic refrigerant mixture as a refrigerant, the refrigerant mixture and the oil have poor compatibility, and an oil that separates into three or more layers even when both are mixed is used as a refrigerating machine oil. HFC characterized by being used
Refrigeration cycle using a non-azeotropic refrigerant mixture. 2. The refrigeration cycle using the HFC-based non-azeotropic refrigerant mixture according to claim 1, wherein the refrigerating machine oil is an oil selected from mineral oil and alkylbenzene-based oil. 3. A refrigeration cycle using an HFC-based non-azeotropic refrigerant mixture according to claim 1, wherein a rotary compressor is used as the compressor and an alkylbenzene-based oil is used as the refrigerating machine oil. 4. A refrigeration apparatus provided with a condenser for condensing and liquefying a refrigerant, an evaporator for evaporating a liquefied refrigerant, a compressor for compressing the evaporated and evaporated refrigerant and discharging it to a condenser,
An HFC-based non-azeotropic refrigerant mixture is used as the refrigerant to be compressed by the compressor, and an oil that separates into three or more layers is used as the refrigerating machine oil even if the refrigerant mixture and the oil have poor compatibility. A refrigerating device characterized by the above. 5. The refrigerating apparatus according to claim 4, wherein the refrigerating machine oil is an oil selected from mineral oils and alkylbenzene oils. 6. The refrigerating apparatus according to claim 4, wherein a rotary compressor is used as the compressor, and an alkylbenzene oil is used as the refrigerating machine oil.