Troubleshooting of clogging failures in refrigerator drying filters:

Case description: The refrigerators for repair are the direct-cooling refrigerators of Shangling and Hualing, and the clogging of the drier filter; the function and structural features of the drier filter; and the exclusion method after the clogged refrigerator drier.

Faulty refrigerator maintenance analysis: In the refrigeration system of the refrigerator, the dry filter is composed of a dryer and a filter and is installed in the liquid pipeline between the condenser outlet and the capillary inlet.

(1) The function of the dry filter

One of the functions of the dry filter is to filter out impurities in the refrigeration system, such as metal shavings, various types of oxides, and dust, to prevent foreign matter from clogging the capillary or damaging the compressor. These debris originate from incomplete parts and the assembly process is not strict, so that external impurities into the cooling pipe or system in the presence of moisture, air or acidic substances produce chemical reactions. These impurities - once they enter the compressor, can make pistons, cylinders, bearings and other serious wear and even stuck; into the motor windings into the terminal, you may damage the winding coil insulation. Short circuit, breakdown occurs; entering the capillary, due to the fine capillary diameter, it is likely to cause blockage without cooling, so it is necessary to filter these impurities.

Another function of the dry filter is to absorb the residual moisture in the refrigeration system, prevent ice blockage, and reduce the corrosion effect of moisture on the refrigeration system.

The dissolution of water in cfc-12 is very small. The solubility in hfl-134a is smaller and decreases with decreasing temperature; therefore when cfc-12 or hfc-134a contains moisture, the refrigerant goes through the capillary When throttling reduces pressure, the temperature drops. The water's solubility in it decreases. The precipitated water freezes and blocks the capillary, causing periodic cooling. The water also reacts chemically with cfc-12, hfc-134a, and ester oils, decomposes hydrochloric acid, hydrofluoric acid, and co2 gas, corrodes refrigeration pipes and compressors, and accelerates the decomposition of cfc-12 and hfc-134a. Causes the insulation of the motor windings to deteriorate or damage the compression hunger: CO2 gas is a non-condensable gas. Its presence will increase the condensing pressure, reduce the cooling efficiency, and increase the energy consumption. For example, if the vacuum of a refrigeration system is not clean enough, the oxygen in the residual gas reacts with hydrochloric acid and copper to produce mechanical chain feeding phenomenon, and the copper pieces are corroded. The reasonable cooperation between the cylinder and the journal and the sigh of the exhaust valve are damaged. Sealing. Significantly reduce the life of the compressor. Therefore, it is necessary to add a dry filter.

(2) Deconstruction of the dry filter

Dry filters used in household refrigerators are divided into two types: one is a single-hole inlet dry filter, and the other two are single-tube; the other is a double-hole inlet. It is made of copper tubes and the two ends of the shell are equipped with filter nets (usually 80 mesh to 120 mesh metal net) and are filled with desiccant. Brazing is used for the connection with the pipe. The desiccant cannot be replaced. When servicing the refrigeration system, it should be replaced with a full replacement.

There are currently many substances that can be used as desiccants, such as anhydrous calcium chloride, silica gel, and molecular sieves. Various desiccant characteristics vary, and the dry filter used in refrigerators uses spherical molecular sieves or special molecular sieve columns due to the higher operating temperatures. It has a strong adsorption effect on the water content in the refrigeration system.

Since the molecular diameter of the water molecule is 2.7-3.0a.cfc-12 and the diameter of the molecule is 4.4a.hfc-134a, the molecular sieve diameter must be 4.2a. Therefore, the molecular sieve must be selected so that the hfc-13 substance and cfc-12 easily pass and the water molecule is adsorbed. Therefore, for the cfc-12 system. Select 4a° molecular sieve (ie xh-5 type) to adsorb moisture and prevent ice blocking.

(3) Dry filter selection and precautions

1) For the hfc-134a system, xh-7 or xh-9 type molecular sieves with molecular diameters between hfc-134a and water are required (the maximum diameter is 3a°. In contrast, the latter has better drying capacity. Larger. Better, but not xh-5. Because xh-5 is different from xh-7 and xh-9 molecular screening materials, they cannot be substituted for each other. The xh-5 type generally divides the sieve by 8g, and the xh-9 type releases the molecular sieve by about 10g. Molecular sieve saturated water absorption rate of 21% to 25%, plus the general atmosphere (relative humidity 50%). The water absorption is only 1/2 of the saturated water absorption car. Therefore 1g molecular sieve can only adsorb about 0.12g of water.

2) Molecular sieves exposed to the atmosphere for a long time must be activated and regenerated before use. The water content after the activation treatment should not exceed 1.5% by weight. General 4a molecular sieve at standard atmospheric pressure. The activation temperature is 450°C to 550°C. The activation time depends on the amount of molecular sieve. The activated molecular sieve should be isolated from the air, such as evacuated plastic bag sealed or sealed in the iron tank, so as to avoid Adsorption of moisture in the air affects the effect of use.

3) The dry filter should be packed in a plastic bag or stored in a dedicated drying box. It should be installed on the refrigeration system as soon as possible after unpacking. More stringent requirements for hfc-134a, unpacking exposed time 20 minutes

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