1.1 Sources of impurities in the refrigeration system

The refrigeration system of the household refrigerator is composed of a compressor, a condenser, an evaporator, a capillary tube and a pipe piece. The sources of impurities in the refrigeration system mainly include the following aspects: 1) Compressor, pipe parts in gold processing and welding process Contains uncleaned iron filings and grease; 2) iron filings and moisture entering the pipeline during the test or filling of the refrigerant; 3) long-term operation of the refrigerator, moisture remaining in the piping system causes corrosion of the pipe wall And produce debris.

1.2 Characteristics and analysis of impurities in refrigeration system

1.2.1 Compressor

The compressor may produce metal debris during gold processing and welding with the refrigeration line. The residual debris inside the compressor will be circulated with the lubricating oil under the high-speed rotating crankshaft. This may be because The iron chip is stuck and the internal motor of the compressor is blocked. The debris causing the dirty discharge of the household refrigerator mainly comes from the exhaust muffler in the compressor and the residual iron scrap in the surrounding area. This part of the iron scrap can directly enter the exhaust pipe and the condensing pipe. Once passed through the filter, the iron filings will be A blockage is formed in the capillary.

In order to reduce material costs and control noise, the structural design of the exhaust muffler and the cylinder block is increasingly used by compressor manufacturers. The disadvantage of this structure is that the muffler cavity is a cavity cast by sand casting, relatively closed, difficult to clean, and the processing debris is easy to remain therein. The threaded hole of the internal exhaust pipe of the fixed compressor usually adopts a blind hole structure, and it is easy to retain metal debris. Therefore, the manufacturing process of the compressor requires a lot of time to control and remove the metal debris, especially in some special locations where metal debris is easily retained (cleaning must be strictly controlled).

1.2.2 Refrigeration pipe fittings

1) Application of single-layer Steel Pipe

At present, single-layer steel pipes have been widely used in the manufacture of household refrigerator pipe fittings. The single-layer steel pipe is a seamed steel pipe formed by cold-rolling steel strip through 360 forming butt welding. During the butt welding process, tiny particles of beads are stuck on the inner wall of the steel pipe. During the process of reducing and drawing the steel pipe and mechanical bending, these tiny particles may fall off, and the refrigerant in the refrigeration system of the household refrigerator The flow of lubricating oil forms a blockage at the capillary.

2) Processing of pipe parts

Household refrigerator refrigeration pipe parts will produce debris during processing such as cutting, flaring, clearing 4 single-layer steel pipe, etc., which will be more or less left in the pipe parts. . Pipe fittings are an important part of the refrigeration system for household refrigerators, which is one of the reasons for the dirty plugging of the refrigeration system. The crumb is curled under the magnifying glass. The enlarged view is shown in Fig. 5. In addition, the lubricating oil used for the flaring, cold drawing and drawing of the pipe parts is increased in viscosity under low temperature conditions, and even the condensation is blocked to block the capillary. . The lubricating oil used in this type of processing must be strictly controlled and cannot enter the inside of the pipe. The residual oil in the pipe must be cleaned with a special cleaning agent.

3) Welding of pipe parts

Welding is one of the indispensable processes in the processing of pipe fittings and the sealing process of household refrigerator refrigeration systems. For example, a single-layer steel pipe used for evaporator production, Fe3O4 is formed on the inner wall during welding, and Fe3O4 is welded during overheating. It will peel off and form debris.

1.2.3 Test leak or charge refrigerant

Household refrigerators also have the possibility of entering iron filings and moisture when using nitrogen to test leaks or to charge refrigerant. Steel cylinders containing nitrogen and refrigerant, including steel pipes for conveying gas, are mostly subjected to water pressure method when performing airtightness test or safety withstand voltage test. The inside of the steel pipe after security inspection is prone to rust and iron filings.

1.2.4 Long-term operation of household refrigerators

During long-term operation of the household refrigerator, moisture remaining in the piping system causes corrosion of the pipe wall, and iron scraping in the rusted area may block the capillary.

2 diagnosis of dirty plugging problem in household refrigerator refrigeration system

When the household refrigerator refrigeration system is dirty, the pressure difference of the refrigeration system becomes larger, and the inlet temperature of the evaporator decreases. However, as the refrigerant flow rate decreases rapidly, the dryness of the refrigerant in the latter half of the evaporator rises. If the compressor is overheated, the compressor may run continuously. The temperature in the freezer compartment may be lower, the temperature in the refrigerator compartment may rise, and the back ice will be uneven after refrigeration. According to the degree of pipe blockage, the degree of power reduction of the compressor is different, but some of the system has too many tiny particles, which makes the friction of the motion pair become larger, and the power of the refrigerator is on the rise.

The dirty plugging of the household refrigerator often occurs at the entrance of the capillary. The filter of the faulty refrigerator is dissected. It may be found that different sizes of debris are distributed on the filter mesh or mesh. The chips are poured out for magnification observation. According to the above description, the root cause of the quality problem is identified, and the control of which link has occurred is determined, and measures are taken in a targeted manner.

It should be added that the material of the cylinder block of the compressor is gray cast iron, and the carbon of the gray cast iron has carbon in the form of graphite. Under the microscope, the processing debris of the gray cast iron and the oxide of the steel pipe are very color. Close, it is easy to mistakenly believe that the evaporator, the condenser overburning residual impurities. Through observation and comparison, there is still a clear difference between them: the iron scrap produced by gold processing is relatively hard, and the scale produced by the evaporator over-burning is easily crushed into a finer powder.

3 a possible solution

3.1 The principle of the solution

Although there are many causes for the formation of dirty plugs in household refrigerators, most of the debris components are ferromagnetic materials that can be adsorbed by magnets.

Even if a small amount of rust formed by the corrosion of the iron pipe cannot be adsorbed by the permanent magnet, the author found that the rust peeled off from the inner wall of the steel pipe often has an iron core that can be adsorbed, so most of the rust can also be adsorbed by the permanent magnet.

Common magnetic materials are barium, barium ferrite, neodymium iron boron, etc. These materials have more Curie points above 500#. As long as the position is properly designed, it is easy to avoid adverse effects such as degaussing caused by high temperature.

3.2 Application of new magnetic filter

The filter can not only effectively reduce the chance of dirty plugging in the household refrigerator, but also solve the problem of the valve plug of the solenoid valve of the refrigerator. Because the solenoid valve used in the refrigerator itself has two pieces of magnetic steel, the iron filings in the pipe are easily accumulated in the vicinity of the valve core, which seriously causes the valve core to be stuck. After using the new magnetic filter, it can effectively absorb the iron filings that may enter the valve core, avoiding the solenoid valve from opening and not reversing, and causing a jam.

4 Conclusion

Dirty blockage of household refrigerator refrigeration system is a kind of refrigeration failure with a very high incidence. Although there are many reasons for the formation of dirty plugging, it is determined that the household refrigerator is dirty by analyzing the source and characteristics of the impurities in the refrigeration system of the household refrigerator. The root of the problem, looking for a possible solution, pointed out the direction for the improvement of the quality level of household refrigerators.

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