Due to the frost on the surface of the evaporator in the cold storage, it prevents the conduction and dissemination of the cold capacity of the refrigeration evaporator (pipeline), and ultimately affects the refrigeration effect. When the thickness of the frost layer (ice) on the surface of the evaporator reaches a certain extent, the refrigeration efficiency even drops to less than 30%, resulting in a large waste of electric energy and shortening the service life of the refrigeration system. Therefore, it is necessary to carry out cold storage defrost operation in the appropriate cycle.
Defrosting purpose
1, improve the refrigeration efficiency of the system;
2. Ensure the quality of frozen products in the warehouse
3, save energy;
4, extend the service life of cold storage system.
Defrosting method
Cold storage defrosting methods: hot gas defrosting (hot fluorine defrosting, hot ammonia defrosting), water defrosting, electrical defrosting, mechanical (artificial) defrosting, etc.
1, hot gas defrost
Suitable for large, medium and small cold storage pipe defrosting directly the hot high temperature gaseous condensate into the evaporator without stopping the flow, the evaporator temperature rises, and the frost layer and the cold discharge joint dissolve or then peel off. Hot gas defrosting is economical and reliable, convenient for maintenance and management, and its investment and construction difficulty is not large. However, there are also many hot gas defrosting schemes, the usual practice is to send the high-pressure and high-temperature gas discharged from the compressor into an evaporator to release heat and defrosting, so that the condensed liquid then enters another evaporator to absorb heat and evaporate into low temperature and low pressure gas, and then returns to the compressor suction port to complete a cycle.
2, water spray defrost
It is widely used for defrosting of large and medium chillers
Periodically spray the evaporator with room temperature water to melt the frost layer. Although the defrosting effect is very good, it is more suitable for air coolers, and it is difficult to operate for evaporation coils. It is also possible to spray the evaporator with a solution with a higher freezing temperature, such as 5%-8% concentrated brine, to prevent frost formation.
3. Electric defrosting
Electric heat pipe defrosting is mostly used in medium and small air cooler; Electric heating wire defrosting is mostly used in medium and small cold storage aluminum tubes
Electric heating defrosting, for the chiller is simple and easy to use; However, for the case of aluminum tube cold storage, the construction difficulty of aluminum fin installation of electric heating wire is not small, and the failure rate is relatively high in the future, the maintenance and management is difficult, the economy is poor, and the safety factor is relatively low.
4, mechanical artificial defrosting
Small cold storage pipe defrosting for cold storage pipe manual defrosting is more economical, the most original defrosting method. Large cold storage with artificial defrosting is unrealistic, the head up operation is difficult, physical consumption is too fast, the retention time in the warehouse is too long is harmful to health, defrosting is not easy to complete, may cause the evaporator deformation, and may even break the evaporator and lead to refrigerant leakage accidents.
Mode selection(Fluorine system)
According to the different evaporator of the cold storage, the relatively appropriate defrosting method is selected, and the energy consumption, the use of safety factor, the installation and operation difficulty are further screened.
1, the defrosting method of the cold fan
There are electric tube defrosting and water defrosting can choose. Areas with more convenient water use can prefer water-flushing frost chiller, and areas with water shortage tend to choose electric heat pipe frost chiller. Water flushing frost chiller is generally configured in large air conditioning, refrigeration system.
2. Defrosting method of steel row
There are hot fluorine defrosting and artificial defrosting options.
3. Defrosting method of aluminum tube
There are thermal fluoride defrosting and electric thermal defrosting options. With the extensive use of aluminum tube evaporator, the defrosting of aluminum tube has been paid more and more attention by users. Due to material reasons, aluminum tube is basically not suitable for the use of simple and rough artificial mechanical defrosting like steel, so the defrosting method of aluminum tube should choose electric wire defrosting and hot fluorine defrosting method, combined with energy consumption, energy efficiency ratio and safety and other factors, aluminum tube defrosting is more appropriate to choose hot fluorine defrosting method.
Hot fluoride defrosting application
A freon flow direction conversion equipment developed according to the principle of hot gas defrosting, or a conversion system composed of a number of electromagnetic valves (hand valves) connected, that is, a refrigerant regulating station, can realize the application of hot fluorine defrosting in cold storage.
1, manual adjustment station
It is widely used in large refrigeration systems such as parallel connection.
2, hot fluorine conversion equipment
It is widely used in small and medium-sized single refrigeration system. Such as: one key hot fluorine defrosting conversion device.
One click hot fluorine defrosting
It is suitable for the independent circulation system of single compressor (not suitable for the connection installation of parallel, multistage and overlapping units). It is used in small and medium-sized cold storage pipe defrosting and ice industry defrosting.
peculiarity
1, manual control, one-click conversion.
2, heating from the inside, the frost layer and the pipe wall can melt and fall, energy efficiency ratio 1:2.5.
3, defrosting thoroughly, more than 80% of the frost layer is a solid drop.
4, according to the drawing directly installed on the condensing unit, do not need other special accessories.
5, according to the actual differences in ambient temperature, it generally takes 30 to 150 minutes.
Post time: Oct-18-2024