JPH0727448A - Freezer device - Google Patents

Abstract

PURPOSE:To prevent a flow rate of refrigerant at an inner surface of a capillary tube from being decreased. CONSTITUTION:A freezer device having a closed freezing cycle is comprised of a refrigerant; a compressing mechanism for compressing this refrigerant from its low pressure to a high pressure; a mechanism for condensing the refrigerant compressed to a high pressure; an expansion mechanism for expanding the condensed refrigerant with a capillary tube; and an evaporating mechanism for evaporating the expanded refrigerant to make refrigerant of low pressure. In this freezer device, the capillary tube is made of an iron metallic material containing chromium(Cr).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus, and more particularly to a refrigerating apparatus capable of reducing corrosion on the inner surface of a capillary tube in a refrigeration cycle and reducing the amount of corrosion products attached.

[0002]

2. Description of the Related Art In a refrigerating apparatus including a refrigerating cycle represented by an air conditioner and a refrigerator, a refrigerant is circulated in a closed system while being evaporated, compressed, condensed and expanded to perform cooling. Such a refrigeration cycle has a heat exchanger,
It is composed of a compressor, a capillary tube and the like, and the material of the constituent parts is mainly copper except for the inside of the compressor in terms of workability, good thermal conductivity and cost. When manufacturing a component like this, if a refrigeration cycle is assembled with a large amount of oil used during cutting, pipe expansion, etc. remaining, the residual oil goes around the refrigeration cycle and accumulates in the capillary tube. Therefore, it leads to a problem that the flow rate of the refrigerant decreases. Therefore, it is necessary to reduce the residuals as much as possible in the manufacturing process of a single product before the refrigeration cycle is assembled. Conventionally, a degreasing cleaning process was provided at the final stage of the single product manufacturing process, and due to its cleanability, good permeability, and difficulty in remaining in parts, CFCs 113, 1,1,1-trichloroethane, and CFCs such as methacrene, Cleaning is done with chlorine-based organic solvents. However, the use of these CFC-based and chlorine-based organic solvents is regulated due to environmental problems such as ozone layer depletion and water pollution. Therefore, a water-soluble alkaline cleaning method or a cleaning-less method, which substitutes for a chlorofluorocarbon-based or chlorine-based organic solvent, is being studied.

[0003]

However, after the inside of the refrigeration cycle using the conventional copper capillary tube is washed with a water-based alkaline cleaner other than a CFC-based or chlorine-based organic solvent, or is frozen without cleaning. When the device is assembled and operated, there is a problem that the refrigerating capacity is deteriorated during the operation.

As a result of investigating the deterioration of the refrigerating capacity, it was found that the refrigerant flow rate was decreased due to the accumulation of foreign matters in the copper capillary tube. Furthermore, when investigating the accumulated foreign matter, it was found that the organic residue such as cutting oil was not accumulated as in the past, but the inorganic residue was mainly composed of copper compounds such as copper oxide. Chlorine (Cl) ions were also detected. Moreover, since the deposits had large irregularities and erosion marks were observed on the surface, it was found that corrosion products with severe irregularities were generated due to the progress of the copper corrosion reaction by chlorine (Cl) ions.

As a result of further investigation on the corrosion reaction of copper, it is considered that the residual water content in the cycle has a large effect, and conventional CFC-based and chlorine-based organic solvents have a water-drying property in addition to degreasing. It was confirmed that It was also found that the amount of residual water increases when washed with a cleaning agent other than a chlorofluorocarbon-based or chlorine-based organic solvent, and the amount of residual water greatly varies depending on the washing process.

Therefore, when cleaning with a cleaning agent other than a CFC-based or chlorine-based organic solvent, the amount of residual water in the cycle increases, which causes chlorine (Cl) ions due to the decomposition of the refrigerant or the decomposition of chlorine-based process auxiliary materials. Is promoted. Chlorine (Cl) ions are also carried to the capillary tube and cause the corrosion reaction of copper. Normally, the copper surface is protected by a natural film, but the flow of refrigerant and chlorine (C
l) It is destroyed by ions, and the surface of the destroyed part becomes active and corrosion (dissolution as ions, redeposition as copper or copper oxide, chloride) proceeds.

In particular, the capillary tube portion has a large flow velocity of the refrigerant as compared with other general pipes and is likely to be turbulent, so that the coating film on the inner surface of the tube is easily broken and the surface is easily activated, so that the reaction proceeds significantly. Dissolution and adhesion of the surface of the capillary tube causes adhesion of corrosion products with large irregularities.

Further, since the capillary tube is usually manufactured by a drawing process, processing scratches are likely to remain,
The adhesion is preferentially generated from the weak portion of the protective film originally due to the processing flaw, and the corrosive substance is easily stopped in the concave portion, so that the corrosion easily progresses.

Further, the adhesion to the capillary surface is not limited to the re-adhesion from the material once eluted from the capillary itself, but the one eluted from the heat exchanger or the pipe may be conveyed and deposited on the capillary tube portion.
Due to the above process, the flow resistance increases, so that the refrigerant flow rate decreases, and the refrigerating capacity decreases. As described above, when the corrosion product having large irregularities is formed in the capillary tube portion, it has a great influence particularly on the deterioration of the refrigerating capacity and causes a problem in durability and reliability of the refrigerating apparatus. In order to solve such a problem, it is necessary to reduce the residual water content in the cycle as much as possible, but it is practically difficult to completely eliminate it.

The present invention has been made to address such a problem, and in the refrigerating cycle of a refrigerating apparatus, it is possible to prevent a decrease in the flow rate of the refrigerant, particularly on the inner surface of the capillary tube, to improve durability and reliability. It is an object of the present invention to provide a refrigerating device that can be used.

[0011]

A refrigerating apparatus of the present invention comprises a compression mechanism for compressing a gaseous refrigerant to a pressure higher than a low pressure, a mechanism for condensing a refrigerant compressed to a high pressure, and a capillary tube for the condensed refrigerant. In a refrigerating apparatus having a closed refrigeration cycle consisting of an expansion mechanism for expanding by means of an expansion mechanism and an evaporation mechanism for evaporating the expanded refrigerant into a low-pressure refrigerant, the capillary tube is made of an iron-based metallic material containing chromium (Cr). It is characterized by

Further, the refrigerating apparatus of the present invention is characterized in that the inner surface of the refrigerating cycle is formed of a resin which is stable with respect to the refrigerant and the refrigerating machine oil.

Further, the inner surface of the capillary tube has a surface roughness (Rmax) of 20 μm or less.

The capillary tube according to the present invention constitutes a portion for changing the pressure of the refrigerant from high pressure to low pressure in the refrigeration cycle. In order to prevent the inner surface corrosion of such a capillary tube, the present invention uses a ferrous metal material containing at least chromium (Cr) as the material to be used. Chrome (C
Other than r), nickel (Ni), molybdenum (Mo), etc. can be contained. As a preferred specific example, SUS304, S
Austenitic stainless steels such as US316 can be mentioned. By using such an iron-based metal material, the passivation film that protects the metal surface is formed more strongly against chlorine (Cl) ions and the flow of the refrigerant than with copper, and thus has excellent corrosion resistance. . In addition, it has excellent workability such as bendability and extensibility required for capillary tubes.

In the capillary tube according to the present invention, it is important that the metal of the inner surface of the capillary tube does not come into direct contact with corrosive substances such as water and chlorine (Cl) ions. Therefore, in another aspect of the present invention, the inner surface of the capillary tube is formed of a resin that is stable against the refrigerant and the refrigerating machine oil. Here, being stable with respect to the refrigerant and the refrigerating machine oil means that the refrigerant and the refrigerating machine oil are not dissolved or cracked when the refrigerating apparatus is operated or stopped. Further, the resin is required to have excellent adhesion to the capillary tube, workability after coating, abrasion resistance, heat resistance and the like. Examples of resins suitable for the present invention include fluororesins such as difluorinated resins and tetrafluorinated resins, epoxy resins, and silicone resins. The effect of the resin coating is effective not only on the capillary tube but also on the inner surface of the entire refrigeration cycle such as the heat exchanger and the piping. When chlorine (Cl) ions and the like locally remain in the heat exchanger, it is possible to prevent an accident such as corrosion, which causes a gas leak.

In still another capillary tube according to the present invention, the inner surface of the tube is made uniform and smooth, and the surface roughness (Rmax) is 20 μm or less. Surface roughness (Rmax)
Is 20 μm or less, the irregularities on the inner surface of the capillary tube can be made smooth. Thereby,
For example, it has been confirmed that the corrosive substance can be suppressed from remaining in a recessed portion such as a processing scratched portion, and that the function of suppressing the progress of corrosion is effective even if the material of the capillary tube is copper. The surface roughness (Rmax) is a value that does not include a waviness portion on the inner surface of the capillary tube.
The method for adjusting the surface roughness (Rmax) to 20 μm or less is not particularly limited, but polishing methods such as mechanical polishing, chemical polishing and electrolytic polishing can be used.

[0017]

[Function] When the capillary tube material is an iron-based metal material containing at least chromium (Cr), a passivation film that is stronger than the copper material is more likely to be formed on the inner surface of the tube, and water or chlorine (Cl) ions Surface corrosion can be prevented.

Further, by forming the resin layer on the inner surface of the capillary tube, it is possible to prevent direct contact between the metal base and the corrosion-causing substance such as chlorine (Cl) ion contained in the refrigerant or the refrigerating machine oil. As a result, the elution of ions from the metal base can be prevented.

Further, if the surface roughness of the inner surface of the capillary tube is 20 μm or less, the corroded surface has less irregularities, so that the causative substance is less likely to stay on the capillary surface and the progress of corrosion can be suppressed.

[0020]

EXAMPLES Examples of the present invention will be described below. Example 1 Stainless steel (SUS316) pipe (internal diameter 1.5 mm, length 1
m) was used as the capillary tube.

The flow rate in the tube was measured in advance by the following method.

Freon 113 was filled in a pressure cylinder and pressurized (2 Kg / cm ² ) with air to flow Freon 113 into a capillary tube and kept at a constant temperature for a fixed time (30
Flow rate was measured.

Next, an air conditioner, which is a refrigerating device having a refrigerating cycle using this capillary tube, is assembled, and Freon 22 as a refrigerant and mineral oil as a refrigerating machine oil are sealed. Further, 5 ml of water was forcibly added to carry out an acceleration test. In the accelerated test, the air conditioner was operated continuously for 12 hours and intermittently for 12 hours as one cycle, until the total cooling operation time reached 500 hours. After completion of the acceleration test, the capillary tube was removed, the flow rate in the tube was measured again under the same conditions as above, and the difference from the value before operation was taken as the flow rate change amount (%) with respect to the value before operation.
The results are shown in Table 1.

Example 2 A copper pipe (internal diameter 1.5 mm, length 1 m) was prepared as a material for a capillary tube. This copper pipe was put into a liquid containing 5 g / l of fluorinated graphite fine powder (average particle size of about 0.2 μm) and a water-soluble fluorocarbon-based cationic surfactant.
Teflon coating was applied to the entire surface of the copper pipe by repeating immersion for 5 minutes and heating at 250 ° C for 10 minutes 5 times. The flow rate change amount was measured under the same conditions as in Example 1 except that this Teflon-coated copper pipe was used as a capillary tube. The results are shown in Table 1.

Example 3 A copper pipe (internal diameter 1.5 mm, length 1 m) was prepared as a material for a capillary tube. This copper pipe is used for 32 volumes of nitric acid (HNO ₃ ), 64 volumes of sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl) 1
Volume and pure water (H ₂ O) 64 volumes mixed solution (Kirinsu) at room temperature
It was immersed for 10 minutes into a capillary tube. The flow rate change amount was measured under the same conditions as in Example 1 except that this capillary tube was used. The results are shown in Table 1. As a result of measuring the surface roughness of the inner surface of this capillary tube, the surface roughness (Rmax) was 15 μm.

Comparative Example 1 A copper pipe (internal diameter 1.5 mm, length 1 m) was prepared as a material for a capillary tube. This copper pipe was used as a capillary tube without any treatment. The flow rate change amount was measured under the same conditions as in Example 1 except that this capillary tube was used. The results are shown in Table 1. As a result of measuring the surface roughness of the inner surface of this capillary tube, the surface roughness (Rmax) was 24 μm.

[0027]

[Table 1] As is clear from Table 1, in Examples 1 to 3, the flow rate change amount was smaller than that in Comparative Example 1, which was within the range of measurement error, and it was found that there was almost no adhesion of corrosion products.

[0028]

According to the refrigerating apparatus of the present invention, the capillary tube is made of an iron-based metallic material containing chromium (Cr), or a resin stable with respect to the refrigerant and the refrigerating machine oil, or the surface roughness of the inner surface of the capillary tube ( Rmax) to 2
Since it is set to 0 μm or less, generation of corrosion products can be suppressed during operation of the refrigeration system.

As a result, it is possible to prevent a decrease in the flow rate of the refrigerant on the inner surface of the capillary tube and improve the durability and reliability of the refrigeration system.

Claims (3)

[Claims] 1. A compression mechanism for compressing a gaseous refrigerant to a high pressure from a low pressure, a mechanism for condensing the compressed refrigerant to a high pressure, an expansion mechanism for expanding the condensed refrigerant by a capillary tube, and the expansion. In a refrigerating apparatus having a closed refrigeration cycle consisting of an evaporation mechanism that evaporates the formed refrigerant to a low-pressure refrigerant, the capillary tube is made of an iron-based metallic material containing chromium (Cr), . 2. A compression mechanism for compressing a gaseous refrigerant from a low pressure to a high pressure, a mechanism for condensing the compressed refrigerant to a high pressure, an expansion mechanism for expanding the condensed refrigerant, and an expanded refrigerant. In a refrigerating apparatus having a closed refrigeration cycle consisting of an evaporation mechanism that evaporates and becomes a low-pressure refrigerant, the refrigeration cycle inner surface is formed of a resin stable to the refrigerant and refrigerating machine oil in the refrigeration cycle. Characterizing refrigeration equipment. 3. A compression mechanism for compressing a gaseous refrigerant to a high pressure from a low pressure, a mechanism for condensing the compressed refrigerant to a high pressure, an expansion mechanism for expanding the condensed refrigerant by a capillary tube, and the expansion mechanism. In a refrigerating apparatus having a closed refrigeration cycle consisting of an evaporation mechanism that evaporates the refrigerant to a low-pressure refrigerant, the surface roughness (Rmax) of the inner surface of the capillary tube is
Refrigeration equipment characterized by having a size of 20 μm or less.