JP2008202813A - Refrigerating cycle device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device having high durability and a long service life even when it is installed under a severe air-conditioning environment. <P>SOLUTION: In this refrigerating cycle device, a refrigerant flow channel 1A constituting a refrigerant circuit 1 is composed of oxygen free copper. A refrigerant pipe 8 of an evaporator 5 of the refrigerant circuit 1 is applied as the refrigerant flow channel 1A composed of oxygen free copper, a temperature-rising part in brazing the refrigerant flow channel 1A is coated with a rust-proof coating film, silver brazing filler metal is applied as brazing filler metal used in brazing the refrigerant flow channel 1A, and hydrogen embrittlement prevention treatment is performed in brazing the refrigerant flow channel 1A. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus including a refrigerant circuit used in, for example, an air conditioner or a refrigeration apparatus, and a method for manufacturing the refrigeration cycle apparatus.

  Conventionally, the refrigerant circuit of this type of refrigeration cycle apparatus has a refrigerant flow path in which a compressor, a condenser, a refrigerant throttle valve, and an evaporator are connected in an annular shape through refrigerant piping. In this refrigeration cycle apparatus, the refrigerant pipe, the condenser refrigerant pipe, and the evaporator refrigerant pipe are made of phosphorous deoxidized copper (JIS-H-3100, alloy number 1201) which is inexpensive and hardly causes hydrogen embrittlement described later. The tubes are connected by brazing.

JP 2002-303428 A

By the way, in an air conditioner installed in an environment where oil mist is generated, such as in a machine processing / food processing factory, etc., a refrigerant made of copper tube is formed by organic acids such as formic acid and acetic acid generated by oxidation of the oil mist. There is a problem in that the refrigerant pipe of the pipe and the heat exchanger is corroded and the life is shortened. In particular, in the case of a conventional evaporator using a phosphorous-deoxidized copper refrigerant tube, the corrosion rate increases rapidly in a specific pH range (especially 2.8 or more and less than 4), and the ant nest shape has a deep erosion depth. It has been conventionally known that corrosion frequently occurs (see curve F in FIG. 4). For this reason, an anticorrosive coating process that increases the production lead time or a copper alloy with poor workability must be used, and thus a device with high corrosion resistance against organic acids has been desired.
Therefore, an air conditioner in which an adsorbent is provided in the indoor unit is described in Patent Document 1 described above. In this air conditioner, the adsorbent adsorbs and removes the organic acid flowing into the indoor unit from the air-conditioning environment, thereby suppressing corrosion of the refrigerant pipe of the heat exchanger. However, since the amount of oil mist flowing from the air conditioning environment described above is very large, the adsorption capacity of adsorbents such as activated carbon is lost in a short period of time, and the adsorbent must be replaced in a short period of time. There was a problem that maintenance work and adsorbent cost were required.

  The present invention has been made in view of the above-described conventional problems, and provides a refrigeration cycle apparatus and a method for manufacturing the same that have high durability and require less labor for maintenance even under severe installation environments. Objective.

  In order to achieve the above object, a refrigeration cycle apparatus according to the present invention is configured such that a refrigerant flow path constituting a refrigerant circuit is made of oxygen-free copper.

  According to the refrigeration cycle apparatus according to the present invention, since the refrigerant flow path of the refrigerant circuit is made of oxygen-free copper, the erosion depth with the passage of time of use is significantly smaller than that of conventional phosphorous deoxidized copper. Moreover, it does not cause a rapid increase in the corrosion rate in a specific pH range. Therefore, frequent occurrence of so-called ant nest corrosion can be prevented, and a refrigeration cycle apparatus with high durability and long life can be provided.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram showing a refrigerant circuit of a refrigeration cycle apparatus according to an embodiment of the present invention.
In FIG. 1, the refrigeration cycle apparatus according to this embodiment shows an example of an air conditioner including a refrigerant circuit 1 that performs a refrigeration cycle operation. In the refrigerant circuit 1, a compressor 2, a condenser 3, a refrigerant throttle valve 4, and an evaporator 5 are connected in an annular manner via refrigerant pipes 7, 7, 7, and 7, respectively. That is, the refrigerant circulation part in the compressor 2, the refrigerant pipe 7, the refrigerant pipe 9 of the condenser 3, the refrigerant pipe 7, the refrigerant circulation part in the refrigerant throttle valve 4, the refrigerant pipe 7, the refrigerant pipe 8 of the evaporator 5, and The refrigerant flow path 1A of the refrigerant circuit 1 is configured by the refrigerant pipe 7 communicating in an annular shape. The evaporator 5 is disposed in an air-conditioning environment A that performs cooling, and is configured, for example, as a fin tube type. The air conditioning environment A is an environment such as a machining factory where oil mist is generated.

In the evaporator 5, as shown in FIGS. 2 and 3, a plurality of fins 10, 10, 10,... (Omitted) is formed. Each fin 10 has a predetermined gap between adjacent fins 10 due to the presence of the collar 15 cut and raised when the tube insertion hole is formed. And the hairpin-shaped piping 11, 11, 11, ... is penetrated from the one end side of a fin assembly to the pipe insertion hole of each fin 10. As shown in FIG. The tube end portions 11A and 11B of each hairpin-shaped pipe 11 are projected from the other end side of the fin assembly, and the tube end portion 11B of a certain hairpin-shaped tube 11 and the tube end portion 11A of the next hairpin-shaped tube 11 are used. Are connected via a U-shaped pipe joint 12. That is, the refrigerant pipe 8 of the evaporator 5 is constituted by the hairpin-shaped pipes 11, 11, 11,... And the pipe joints 12, 12, 12,. In this embodiment, the hairpin-shaped pipe 11 and the pipe joint 12 are made of oxygen-free copper (JIS-H-3100, alloy number C-1020).

And the pipe end part 11B and the pipe end part 11A of the hairpin-like pipes 11 and 11 are respectively inserted into the large diameter parts 13 and 13 at both ends of the pipe joint 12, and the insertion part and its vicinity are heated to about 800 ° C. After that, brazing (brazing unit 14) is performed. The brazing material used for such brazing is not particularly limited as long as it has a melting point of 450 ° C. or higher used in so-called hard brazing. Examples of such a brazing material include silver brazing, gold brazing, brass brazing, brass brazing, nickel brazing, and aluminum brazing. In this embodiment, for example, silver wax is used.

Next, the cooling operation of the refrigerant circuit 1 of the air conditioner configured as described above will be described. The high-temperature and high-pressure gas refrigerant discharged from the compressor 2 flows into the refrigerant pipe 9 of the condenser 3 and is cooled by the outdoor air to be condensed and liquefied. The refrigerant discharged from the condenser 3 is decompressed by the refrigerant throttle valve 4 and flows into the refrigerant pipe 8 of the evaporator 5. In the evaporator 5, the refrigerant cools the air in the air-conditioning environment A and evaporates in the refrigerant pipe 8 and exits the evaporator 5. The gas refrigerant flowing out of the evaporator 5 returns to the compressor 2 through the accumulator 6. Such a refrigeration cycle operation is repeated.
In the refrigerant circuit 1, moisture in the air of the air-conditioning environment A is condensed on the surface of the refrigerant pipe 8 of the evaporator 5 and is dripped and drained as drain water. In this case, if the air-conditioning environment A is an environment such as a machining / food processing factory where oil mist is generated, the surface of the refrigerant pipe 8 has a low pH (that is, acidic) due to formic acid, acetic acid, etc. generated by oxidation of the oil mist. It is often in a wet state.

FIG. 4 is a graph showing the relationship between the pH and the erosion rate in a humid environment of the evaporator refrigerant pipe portion obtained in the test. Here, E shows the state of oxygen-free copper, and F shows the state of phosphorus deoxidized copper. As shown in this graph, in the case of oxygen-free copper, the erosion rate gradually increases as the pH decreases. On the other hand, in the case of phosphorous deoxidized copper, the erosion rate rapidly increases in a specific pH range (especially 2.8 or more and less than 4), and so-called ant nest corrosion progresses.
FIG. 5 is also a graph showing the relationship between the elapsed time and the erosion depth in the humid environment of the evaporator refrigerant tube portion obtained at the laboratory level (acceleration test). The environment of the test room is a pH environment (especially 2.8 or more and less than 4) in which ant nest corrosion tends to proceed. Here, G shows the state of oxygen-free copper, and F shows the state of phosphorus deoxidized copper.
That is, in the refrigeration cycle apparatus of this embodiment, as indicated by the curve G in the graph of FIG. 5, even after 40 days have passed since the start of the acceleration test, the erosion depth of pitting corrosion does not increase to about 100 to 200 μm. The extremely durable evaporator 5 can be provided. In general, ant nest-like corrosion is likely to occur on the surface of the refrigerant pipe facing the collar 15 of the fin 10 with a minute gap, but in the refrigerant pipe 8 of this embodiment, the ant There is almost no nest-like corrosion or pitting corrosion.
On the other hand, as shown by the curve H in the graph, the refrigerant pipe of the conventional general-purpose evaporator has exhibited a large erosion depth particularly from the beginning of the acceleration test, particularly with respect to the ant nest-like corrosion. On the day, the erosion depth reached approximately 600 to 1200 μm, which is about 6 times deeper than that of the refrigerant pipe 8 of the present embodiment. If the corrosion of the refrigerant pipe reaches a deep erosion depth as described above, it is predicted that the erosion depth is equal to (penetrates) the initial pipe wall thickness of the refrigerant pipe from the viewpoint of the pressure resistance of the refrigerant pipe. In a short period before the number of days B, the conventional evaporator will have a lifetime.

And in this embodiment, when brazing the hairpin-shaped piping 11 and the pipe joint 12 of the refrigerant pipe 8 mentioned above, the hydrogen embrittlement prevention process was performed. Here, hydrogen embrittlement refers to a phenomenon in which hydrogen enters the material and becomes brittle. Therefore, the hydrogen embrittlement prevention process is a process for preventing the entry of hydrogen during brazing. As an example of this hydrogen embrittlement prevention treatment, for example, after reaching 800 ° C., the brazing operation time is 60 seconds or less (more preferably 20 seconds or less. Further, the general operation time is 10 seconds or less. .). The brazing operation time here refers to heating a pipe (here, a copper tube having an outer diameter of 7.94 mm and a wall thickness of 0.25 mm) with a torch for heating, and a certain constant temperature, for example, 800 It is the time from the introduction of the brazing material to the removal of the torch and the stop of heating after reaching the temperature. When the heating temperature is high, the brazing time is further shortened.
Therefore, the number of voids (holes) generated on the surface of the refrigerant tube 8 after the heat release to room temperature after brazing was counted. A curve I in the graph of FIG. 6 shows the relationship between the brazing operation time and the number of voids generated on the surface of the refrigerant pipe 8 after brazing. The number of voids is the number per 250 × 250 μm counted by observing the sample surface with a microscope. That is, as is clear from curve I, when the brazing operation time is performed for 60 seconds or less, the generation of voids as the starting point of hydrogen embrittlement cracking is suppressed, and the problem of reduced pressure strength due to hydrogen embrittlement is solved. can do.

Usually, when the heating temperature is inappropriate or when the amount of brazing material is not appropriate, the brazing is reworked by heating to 800 ° C. again. Therefore, as another example of the hydrogen embrittlement prevention treatment, reworking of brazing is performed up to two times. That is, as can be seen from the graph of FIG. 7, if the brazing reworking operation is performed up to two times, generation of voids can be prevented.

  Further, it is known that hydrogen embrittlement occurs in the presence of oxygen. Therefore, as some other examples of the hydrogen embrittlement prevention process, brazing is performed in a container filled with nitrogen gas, and brazing is performed while flowing nitrogen gas toward the brazed portion of the refrigerant pipe. Examples thereof include a treatment and a treatment of brazing in a vacuumed container. These processes can also prevent the generation of voids.

By the way, the portion of the refrigerant pipe 8 that has been heated during brazing loses the characteristics of oxygen-free copper due to thermal oxidation. Thus, the part which heats up at the time of brazing is the brazing part 14 which connected the hairpin-shaped piping 11 and the pipe joint 12, for example, and the hairpin-shaped piping 11 and the pipe joint 12 of the brazing part 14 vicinity. Therefore, as shown in FIG. 8, a rust preventive paint is applied to the surface of these temperature rising portions and coated as a rust preventive coating film 16. Thereby, corrosion of brazing part 14 and refrigerant pipe 8 of the neighborhood can be prevented. The anti-corrosion paint is not particularly limited as long as the coating film has high anti-rust and durability properties and can be easily applied. For example, an epoxy resin paint, a tar epoxy resin paint, an acrylic resin paint, Examples thereof include alkyl silicate resin paints.

Further, in this embodiment, since the silver brazing material having high corrosion resistance and containing no phosphorus is used as the brazing material, it does not impede the characteristics of the oxygen-free copper of the refrigerant pipe 8 and has an anticorrosive effect by brazing the pipes. Decline can be prevented.

In the above-described embodiment, the refrigerant pipe of the evaporator is illustrated as the part made of oxygen-free copper. However, the present invention is not limited thereto, and for example, the refrigerant circulation part of the compressor, the refrigerant pipe of the condenser Needless to say, the components of the refrigerant flow path, such as the refrigerant flow part of the refrigerant throttle valve, the refrigerant pipe of the evaporator, or the refrigerant pipe connecting the respective parts, may be made of oxygen-free copper as much as possible.
Moreover, although the air conditioning apparatus was illustrated as an example of the refrigerating cycle apparatus in the above, this invention is not restricted to an air conditioning apparatus, It can apply also to a freezing apparatus and a refrigerator.

It is a schematic block diagram which shows the refrigerant circuit of the refrigerating-cycle apparatus which concerns on one Embodiment of this invention. It is a schematic front view which shows the evaporator of the said refrigeration cycle apparatus. It is a partial front view including the partial cross section which shows the connection aspect of the refrigerant pipe of the said evaporator. It is a graph which shows the relationship between the corrosion rate regarding the refrigerant | coolant tube | pipe of the said evaporator, and pH of a dew condensation environment. It is a graph which shows the relationship between the erosion depth regarding the refrigerant pipe of the said evaporator, and use elapsed time. It is a graph which shows the relationship between the time required for brazing of the said refrigerant | coolant pipe | tube, and the number of the voids which generate | occur | produced after that. It is a graph which shows the relationship between the number of times of reworking brazing in the refrigerant pipe and the number of voids generated thereafter. It is a partial front view including the partial cross section of the part heated up at the time of brazing of the said refrigerant | coolant pipe | tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigerant circuit, 1A Refrigerant flow path, 5 Evaporator, 7 Refrigerant piping, 8 Refrigerant tube, 11 Hairpin-shaped piping, 12 Pipe joint, 14 Brazing part, 16 Antirust coating, A Air-conditioning environment.

Claims (5)

A refrigeration cycle apparatus characterized in that a refrigerant flow path constituting a refrigerant circuit is made of oxygen-free copper. 2. The refrigeration cycle apparatus according to claim 1, wherein the refrigerant flow path made of oxygen-free copper is a refrigerant pipe of an evaporator of a refrigerant circuit. The refrigeration cycle apparatus according to claim 1 or 2, wherein a temperature rising portion at the time of brazing of the refrigerant flow path is covered with a rust preventive coating. The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the brazing material used for brazing the refrigerant flow path is silver brazing. A method for manufacturing a refrigeration cycle apparatus, wherein hydrogen embrittlement prevention treatment is performed when brazing the refrigerant flow path according to the refrigeration cycle apparatus according to any one of claims 1 to 4.

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