What is a cold storage
The main content of storage and preservation is preservation, that is to say, to keep the original quality and freshness of some agricultural products for a long time, that is, fresh agricultural products. After a period of preservation and storage, they are still fresh or close to the fresh state and quality when they are just picked.
The relationship between temperature and preservation of agricultural products:
After harvest, agricultural products are still a living body. In the process of storage, if they want to maintain their life, they need to consume their own storage nutrition, thus gradually losing their nutritional value and fresh quality. In addition, pests will also take the storage nutrition of agricultural products as food, which will result in the deterioration of agricultural products, loss of freshness and edible value. Temperature is the most important factor to keep the nutrition and fresh quality of agricultural products. Generally speaking, the lower the temperature, the less the nutrition consumption of the product, the worse the disease and insect damage, and the longer the time to keep the fresh quality. At the same time, the smaller the temperature change, the better the preservation effect. The fresh-keeping temperature is not unlimited low, because when the temperature is too low for the product to bear, there will also be cold damage or freezing damage. Therefore, a relatively stable and suitable low-temperature condition is required for preservation and storage. The most suitable temperature for the preservation of most agricultural products is about 0 ℃.
The optimum temperature for keeping agricultural products fresh and stored:
The temperature changes with the seasons of a year and the time of the day. The temperature of most agricultural products in the season of conventional cultivation and harvest is high, and the day and night change greatly, which is not suitable for the preservation and storage of products. Many simple methods are to find a place with low and stable natural temperature to store agricultural products, so as to extend the preservation period of products, such as caves, earth cellars, shady places, etc. these methods can not control the temperature arbitrarily, the preservation effect is poor, and the preservation period is relatively short. In order to meet the requirements of long-term preservation and storage of products, the final solution is to create a relatively stable low-temperature condition manually, that is, through mechanical equipment and electronic instruments, within a certain range, the temperature can be controlled artificially. Common refrigerators are such a facility.
What is cold storage:
Cold storage, generally refers to facilities that use various equipment to cool, control and maintain stable low temperatures. Its basic components are refrigeration system; electric control device; storehouse with certain thermal insulation performance; attached buildings, etc. The refrigeration system mainly includes all kinds of refrigeration equipment. The refrigeration equipment is the heart of the cold storage, which makes the cooling capacity and ensures the supply of cold source in the warehouse. The electronic control device is the brain of the cold storage, which commands the refrigeration system to ensure the supply of cooling capacity. The storehouse with certain heat insulation performance is the place for storing fresh agricultural products. Its function is to keep the stability of the low temperature environment. Generally speaking, the heat insulation performance is called heat preservation. The good heat insulation structure of the warehouse can keep the cooling capacity of the refrigeration equipment manufacturers in the warehouse to the maximum extent and leak out less. On the contrary, it is to minimize the heat leakage out of the warehouse to the warehouse, which is also the main difference between the cold warehouse and the general house.
Selection and construction of cold storage types and rural areas: there are many kinds of cold storage in China, and there is no unified standard for classification. According to the common types of origin, it is briefly introduced as follows:
(1) According to the storage capacity, it can be divided into large, medium and small. Generally speaking, commercial large and medium-sized warehouses have large storage capacity. According to the characteristics of small refrigerators in China and the customary appellation of the masses, the warehouses with a capacity of more than 1000 tons can be called large warehouses, the warehouses with a capacity of fewer than 1000 tons and more than 100 tons can be called medium warehouses, and the warehouses with a capacity of fewer than 100 tons can be called small warehouses. The country of origin is most suitable for the construction of 10-100 tons of small refrigerators.
(2) According to the refrigerants used in the refrigerator, it can be divided into two parts: ammonia refrigerator and fluorine refrigerator.
(3) According to the temperature of cold storage, there are two kinds of cold storage: low-temperature storage and high-temperature storage. The fresh-keeping storehouse of aquatic products and meat is a low-temperature storehouse, the temperature is below – 18 ℃.
(4) According to the form of the cold distributor in the cold storage, there are the exhaust pipe cold storage and the cold fan cold storage. Fruits and vegetables are usually kept fresh in cold air storage, commonly known as cold air storage.
(5) According to the construction mode of a warehouse, it is divided into civil cold storage, assembly cold storage and civil assembly compound cold storage. The civil cold storage is generally a sandwich wall thermal insulation structure, covering a large area and a long construction period. The early cold storage is this way. Prefabricated cold storage is a prefabricated warehouse with prefabricated insulation board, which is short in the construction period and can be disassembled, but with a large investment. The construction and assembly of composite cold storage, the bearing and outer structure of the storeroom is the form of civil engineering and the insulation structure in the form of polyurethane foam spray or polystyrene foam board assembly.
Refrigeration equipment for small refrigerators:
Refrigeration equipment is the heart of cold storage, which is very important. The most critical condition for the operation effect of cold storage is the refrigeration equipment. The main body of the refrigeration equipment is the refrigerator, which has many kinds. There are two kinds of refrigerants: ammonia machine and fluorine machine. Some fluorine machines are general models of various refrigerants. Advanced fluorine machines use R22 and other new refrigerants which have little impact on the environment. Fluorine machine is generally small in size, low in noise, safe and reliable, high in automation and wide in the application, which is suitable for small rural cold storage. The combination of refrigerator, condenser and other equipment is often called a refrigeration unit, which is divided into a water-cooled unit and air-cooled unit. The air-cooled unit is the preferred form of small cold storage, which is simple, compact, easy to install, easy to operate and auxiliary