Combined with the example of cold storage engineering rectification, I will tell you the technology of cold storage defrosting.
Composition of cold storage equipment
The project is a fresh-keeping cold storage, which is an indoor assembled cold storage, consisting of two parts: a high-temperature cold storage and a low-temperature cold storage.
The entire cold storage is provided by three JZF2F7.0 Freon compressor condensing units, the compressor model is 2F7S-7.0 open piston single-unit refrigeration compressor, the cooling capacity is 9.3KW, the input power is 4KW, and the speed is 600rpm. The refrigerant is R22. One of the units is responsible for high-temperature cold storage, and the other two units are responsible for low-temperature cold storage. The indoor evaporator is a serpentine coil attached to the four walls and the top of the cold storage. The condenser is a forced air cooled coil unit. The operation of the cold storage is controlled by the temperature control module to start, stop and run the refrigeration compressor according to the upper and lower limits of the set temperature.
General situation and main problems of cold storage
After the cold storage equipment is put into use, the indicators of the cold storage can basically meet the requirements of use, and the operating parameters of the equipment are also within the normal range. However, after the equipment has been in operation for a period of time, when the frost layer on the evaporating coil needs to be removed, due to the design The solution does not have an automatic cold storage defrosting device, and only manual cold storage defrosting can be performed. Since the coil is located behind the shelves or goods, the shelves or goods must be moved for each defrosting, which is very inconvenient, especially when there are many goods in the cold storage. The defrosting work is even more difficult. If the necessary rectification is not carried out on the cold storage equipment, it is bound to seriously affect the normal use of the cold storage and the maintenance of the equipment.
Cold storage defrosting rectification plan
We know that there are many ways to defrost cold storage, such as mechanical defrosting, electrical defrosting, water spray defrosting and hot air defrosting, etc. The mechanical defrosting mentioned above has a lot of inconvenience. Hot gas defrosting is economical and reliable, easy to maintain and manage, and its investment and construction are not difficult. However, there are many solutions for hot gas defrosting. The usual method is to send the high-pressure and high-temperature gas discharged from the compressor to an evaporator to release heat and defrost, and let the condensed liquid enter another evaporator to absorb heat and evaporate into low-temperature and low-pressure gas. Return to the compressor suction to complete a cycle. Considering that the actual structure of the cold storage is that the three units work relatively independently, if the three compressors are to be used in parallel, many components such as pressure equalizing pipes, oil equalizing pipes, and return air headers must be added. The construction difficulty and engineering amount are not small. After repeated demonstrations and scrutiny, it was finally decided to mainly adopt the principle of cooling and heating conversion of the heat pump unit. In this rectification plan, a four-way valve is added to complete the change of the refrigerant flow direction during the defrosting of the cold storage. During defrosting, a large amount of refrigerant in the liquid storage tank below the condenser enters the condenser, causing the liquid hammer phenomenon of the compressor. A check valve and a pressure regulating valve are added between the condenser and the liquid storage tank.After the rectification, after a month of trial operation, the expected effect was basically achieved on the whole. Only when the frost layer is very thick (average frost layer > 10mm), if the defrosting time is within 30 minutes, the compressor sometimes has a weak By shortening the defrosting cycle of the cold storage and controlling the thickness of the frost layer, the experiment shows that as long as the defrosting is half an hour a day, the thickness of the frost layer will basically not exceed 5mm, and the above-mentioned compressor liquid shock phenomenon will basically not occur. After the rectification of the cold storage equipment, not only greatly facilitated the defrosting work of the cold storage, but also improved the working efficiency of the unit. Under the same storage capacity, the working time of the unit has been significantly reduced compared with the past.
Post time: Mar-10-2023