The purpose, method and choice of cold storage system defrosting

The purpose, method and choice of cold storage system defrosting

I. Overview:

　　 Because the surface of the evaporator in the cold storage is frosted, it hinders the conduction and dissipation of the cold capacity of the refrigeration evaporator (pipe), and z* eventually affects the cooling effect. When the thickness of the frost layer (ice layer) on the surface of the evaporator reaches a certain level, the refrigeration efficiency even drops below 30%, resulting in a large waste of electricity and shortening the service life of the refrigeration system. Therefore, it is necessary to perform cold storage defrosting operations within an appropriate period.

　　 2. Purpose of defrosting:

　　 1. Improve system refrigeration efficiency;

　　 2. Guarantee the quality of frozen in the warehouse;

　　3, save power;

　　 4. Extend the service life of the cold storage system.

　　 3. Defrosting method:

　　 Cold storage defrost methods: hot gas defrost (hot fluorine defrost, hot ammonia defrost), water spray defrost, electrical defrost, mechanical (manual) defrost, etc.

　　 Hot gas defrosting---applicable to defrosting of large, medium and small cold storage pipes 　　 The hot, high-temperature gaseous condensate directly enters the evaporator without interception, and the temperature of the evaporator rises, which promotes the melting or peeling of the junction between the frost layer and the cold row. Hot gas defrost is economical and reliable, maintenance and management are convenient, and its investment and construction are not difficult.

　　Water spray defrosting---mostly used in large and medium-sized air coolers for defrosting

　　 Regularly spray the evaporator with water at room temperature to melt the frost layer. Although water spray defrosting has a good defrosting effect, it is more suitable for air coolers, and it is difficult to operate for evaporating coils. You can also spray the evaporator with a solution with a higher freezing temperature, such as 5% - 8% concentrated brine, to prevent the formation of frost.

　　Electric heating defrosting---electric heating tubes are mostly used for medium and small air coolers

Electric heating wire is mostly used for electric heating and defrosting of aluminum tube in small and medium-sized cold storage. It is simple and easy to use for air coolers. However, for aluminum tube cold storage, it is not easy to install the heating wire on aluminum fins. In the future, the failure rate is also relatively high, the maintenance and management are difficult, the economy is also poor, and the safety factor is relatively low.

　　 Mechanical manual defrosting---applicable for defrosting of small cold storage pipes

　　It is more economical to manually defrost the cold storage pipes, which is the original defrosting method. It is unrealistic to use manual defrosting for larger cold storages. It is difficult to operate with head upwards, too fast physical energy consumption, too long staying in the warehouse is harmful to health, defrosting is not easy to complete, and it may cause deformation of the evaporator, or even damage the evaporation The device leads to a refrigerant leakage accident.

　　 Four, fluorine system defrosting method selection:

　　 Choose a relatively suitable defrosting method according to the different evaporators of the cold storage. A few micro and small cold storages use the door to stop and open the door, using air heat to naturally defrost. Some high-temperature storage coolers choose to stop the refrigerator, turn on the cooler fan separately, use the fan to circulate air to defrost, and do not use the electric heating tube to achieve the purpose of energy saving.

　　 1. Defrosting method of air cooler:

　　A. There are electric heating tube defrosting and water frosting to choose from. In areas where water is more convenient, you can choose water frosting air coolers, and water shortage areas prefer to choose electric heating tube defrosting air coolers.

　　B. Electric heating tube defrosting is mostly used in small air coolers for defrosting; water flushing air coolers are generally deployed in large air conditioning and refrigeration systems.

　　2. Defrosting method of steel row: There are hot fluorine defrosting and manual defrosting to choose from.

　　3. Defrosting method of aluminum tube: There are hot fluorine defrosting and electric defrosting to choose from.

　　 5. Defrosting time of cold storage:

　　 Now most cold storage defrosts are controlled according to the defrost temperature probe or the defrost time. The number of defrosting times, time, and defrosting stop temperature should be adjusted according to the number of stacked goods and the quality of the goods.

　　 At the end of the defrosting time and the dripping time, the fan starts again. Note that the defrosting time should not be too long, try to achieve a reasonable defrosting. (The defrost cycle is generally based on the power supply time or the compressor startup time.)

　　 Six. Analysis of the reasons for excessive frost:

　　 There are many reasons that affect frosting, such as: evaporator structure, atmospheric environment (temperature, humidity) and air flow rate. The order of influence on frost formation and air cooler performance is:

　　 1. The temperature difference between the inlet air and the cold storage air cooler;

　　2, the humidity of the inhaled air;

　　3, fin spacing;

　　 4. Inlet air flow rate.