Frozen warehouse solution

1 quick frozen library overview

The temperature of the quick freezing storehouse is -30 DEG C to -35 DEG C. Quick frozen warehouse is mainly used in food, medicine, medicinal materials, chemical raw materials, such as low temperature freezing.
The so-called frozen, refers to the rapid food through its largest ice crystal formation area, when the average temperature of -18 DEG C when the rapid freezing method. The change will occur in a variety of food in the freezing process, such as physical changes (volume, thermal conductivity, specific heat, dry consumption changes) and chemical changes (protein denaturation, discoloration etc.), tissue changes and biological and microbiological changes etc.. The characteristic of fast frozen food is to maintain the original nutritional value and color of food. In other words, in the freezing process must ensure that the food produced by the above changes to achieve maximum reversibility.
Quick frozen foods have the following advantages:
(1) to avoid the formation of large ice crystals between cells
(2) to reduce the amount of water in the cell analysis, thawing less juice loss
(3) the concentration of solute and food tissue, the contact time of colloid and various components were significantly shortened, and the concentration was reduced to the lowest degree
(4) the food is rapidly reduced to the microbial growth activity temperature, which is favorable to resist the growth of microorganism and its biochemical reaction
(5) in food freezing equipment in the short residence time, began to freeze is conducive to improve the utilization rate and the continuous production equipment most of the food is reduced to -1 DEG C when the temperature generated most ice crystals between -1 to -5 DEG C, this is called the highest ice crystal formation stage. Rapid freezing can shorten the freezing time of this stage, it can eliminate the heat in the fastest speed, which is of great significance to improve the quality of quick-frozen food.
2 refrigeration system part
Library body insulation system: polyurethane cold storage board + automatic return cold storage door or translational cold storage door

Selection of refrigeration units:
According to the differences between China's geographical environment, climate temperature, north is cold, windy weather more, air cooling fast, should use air-cooled refrigeration unit; higher temperatures in southern region, water quality is not easy to scale, and the water temperature in the above freezing, can take chillers, heat fast, high efficiency.
Large cold storage should use evaporative condenser, evaporative condenser combined with air cooling and water cooling mode, combining the advantages of both.
The low temperature refrigeration compressor usually adopts the semi closed piston compressor or the screw compressor.
Selection of indoor cooling mode:
Cold cooling is an integral part of the cold storage refrigeration system, and it can be divided into two ways from the angle of the cold effect. Indirect cooling mode is refrigerant two refrigeration using ethylene glycol, water, energy loss is large, besides using the cold ammonia refrigeration system recommended direct cooling method.
Direct cooling means that the refrigerant absorbs the heat of the cooled object or the inside of the evaporator directly.
Characteristics of direct cooling:
The refrigerant in the evaporator directly boiling heat absorption, phase change, the heat transfer temperature difference is only once, the energy loss is small;
Compared with the direct cooling system, the system is simple, easy to operate and manage, the initial investment and operating costs are lower;
Direct cooling method is widely used because of its low cost, convenient management, long service life and so on.
Selection of cooling equipment
Cold storage is usually used to cool the exhaust pipe, the cold air machine and shelf type pipe cooling equipment, the choice of whether it is directly related to the quality of the cold processing and production efficiency, as well as recurrent costs. Should be taken into account the requirements of cold working process and storage conditions, the occupation area of the warehouse and other factors. Different types of cold storage, cold storage refrigeration equipment is also different.
Generally, the cooling pipe is used as the cooling equipment. Cold storage should use natural convection cooling mode, can effectively guarantee the quality of food, reduce energy consumption; mainly used for storage of frozen meat, poultry, aquatic products, etc.. The utility model can also be used as a substitute for the cooling and exhaust pipe by the breeze speed cooling machine, which is favorable for shortening the construction period and is convenient for automatic control.
Selection of defrosting scheme
Cold storage defrosting is mainly due to the cold storage evaporator surface frost, reduce the humidity inside the refrigerator, hinder the heat conduction of the pipeline, affect the cooling effect. There are three kinds of defrosting measures in cold storage: water spray defrosting, electric defrosting and hot air defrosting.
Spray defrosting: regular water spray cooling evaporator, to prevent the formation of frost layer; spray defrosting, although the effect is very good, but it is more suitable for air cooler, for evaporation coil, it is difficult to operate. There is also a solution with a higher temperature of the freezing point, such as 5%---8% brine spray to prevent frost formation.
Electric defrosting: electric heater defrosting. Although simple, but according to the actual structure and the bottom end of the cold storage usage, the difficulty of construction installation of the electric heating wire is not small, but after the failure rate is relatively high, maintenance is difficult, the economy is poor.
Hot gas defrost: direct gaseous heat into the condensing agent and flows through the evaporator, when the cold storage temperature increased to 1 DEG C when the compressor is shut down. The temperature of the evaporator is increased, which makes the frosting layer melt or peel off; the hot melt defrosting is economical and reliable, the maintenance and management is convenient, and the investment and construction difficulty is not great. But there are a lot of hot gas defrosting scheme, the usual practice is to high temperature and high pressure gas compressor discharge into an evaporator to heat defrosting, let the condensed liquid and then enter another evaporator evaporation into the low temperature and low pressure gas, and then back to the compressor suction to complete a cycle.
Use water spray defrosting method for cooler low temperature cold storage using the recommended air cooler; use pipe for low temperature cold storage cooler, small refrigerator below 100m2 can defrost electric heaters, more than 100m2 of the exhaust pipe should be used in cold hot Freon defrost.
3 automatic control scheme selection
After the automatic control system is used in cold storage, it has obvious advantages in energy saving, safety and reducing the quality of stored food. What kind of automation scheme should be taken into account in terms of investment, annual operating cost and economic benefit. The small and medium-sized refrigeration system is in order to protect the safety of refrigeration equipment control, automatic control of local loop, the general use of microcomputer intelligent controller; the PLC programmable control system for large refrigeration system, automatic control with computer.