The factors of energy consumption of the cold storage mainly include the performance of the refrigeration system of the cold storage, the selection of the refrigerant, the selection of the compressor condenser and the evaporator, the scale and layout of the cold storage, the type and thickness of the insulation layer of the cold storage, and the amount of goods entering and leaving the cold storage. The number of times, the thermal insulation performance of the outer door of the cold storage, etc., to improve the refrigeration efficiency of the cold storage, all factors should be taken into account.
The way to reduce energy consumption of energy-saving cold storage is usually divided into two parts: 1) reducing the cooling load of cold storage, (2) selection of cold storage equipment.
Ⅰ. The energy-saving fruit and vegetable cold storage of fruit and vegetable cold storage refers to the storage board, refrigeration unit, evaporator, etc. that make up the cold storage are pre-manufactured in the factory. And the storage capacity is generally less than 200m3, which is used for cold storage for fresh-keeping storage. According to the design temperature classification, Rruit-vegetable micro cold storage belongs to high temperature cold storage. Micro cold storage is composed of refrigeration system, warehouse, control system and so on.
Factors of energy consumption and energy-saving measures of cold storage for fruits and vegetables
1. Enclosure structure of cold storage The cooling capacity of the cold storage through the enclosure is proportional to the unit heat flow of the enclosure of the cold storage. Therefore, more efforts should be made to reduce the unit heat flow index of the cold storage enclosure of the cold storage. To reduce the unit heat flow of the building envelope, firstly, the thermal conductivity of the thermal insulation material should be small, and secondly, the envelope layer should be thicker. However, the thickness should not be too thick in general, otherwise there will be problems such as increasing the construction cost and wasting space. Therefore, the insulation material should be selected within the appropriate thickness range. Under normal circumstances, the thermal conductivity of the thermal insulation material is required to be low, the water absorption rate is low, the low temperature resistance is good, and the cost cannot be too high. Commonly used cold storage insulation materials are rice husk, polystyrene foam, polyurethane rigid foam and so on. Rice husks are easy to obtain, but the thermal resistance is small, easy to absorb moisture, and the amount is large. The construction of the warehouse is labor-intensive and time-consuming. Large, moderate price, easy to build and install; polyurethane rigid foam has the largest thermal resistance and the best thermal insulation performance, but the price is high.
2. Moisture-proof and vapour-proof of the cold storage enclosure It is also necessary to take moisture-proof and vapour-proof measures for the cold storage enclosure, otherwise the thermal insulation performance of the thermal insulation material will be deteriorated. This is also the reason why the thermal insulation performance of the cold storage body is good when it is first used, but the thermal insulation effect deteriorates after a period of time. Since water vapor permeates from the high temperature side to the low temperature side, the moisture-proof and vapor barrier layer should be located on the side with the highest temperature of the thermal insulation layer.
3. Evaporation pressure and temperature of cold storage Evaporation temperature corresponds to evaporation pressure. After knowing the evaporation pressure, the evaporation temperature can be obtained by looking up the table. Under the condition that the temperature of the cold storage room is constant, the temperature difference (the difference between the evaporation temperature and the temperature of the warehouse) is reduced, the evaporation temperature can be increased accordingly, and the cooling capacity of the cold storage refrigerator will be increased, that is, the circulation efficiency will be improved. Correspondingly Electricity is also saved.
4. Defrost operation in cold storage Generally speaking, when the resistance of the frost layer on the surface of the evaporator to the air is not significant, and the flow of air through the evaporator has not been reduced, the effect of the frost layer is not serious, and it is not necessary to defrost; When the flow of air is significantly reduced, defrosting should be performed. The higher the humidity of the air, the greater the temperature difference between the evaporator and the refrigerator, the easier it is to form frost on the evaporator. Combined with the preservation process, packaging and refrigeration can reduce the dry consumption of fruits and vegetables and reduce the number of defrosting times of the evaporator. In fact, it also plays a role in energy saving of cold storage.
5. Cold storage temperature and cold storage warehouse utilization Different fruits and vegetables have different storage temperatures, and each fruit and vegetable also has a suitable temperature range for its storage. Without affecting the quality of fruits and vegetables, energy-saving cold storage should choose a higher storage temperature. When the temperature of the cold storage is high, the evaporating temperature of the refrigeration system is also increased accordingly, the cooling capacity of the refrigerator will be increased, and the cycle efficiency will of course be improved. More importantly, increasing the temperature of the cold storage can also reduce the heat transfer to the outside through the storage body. The utilization rate of energy-saving cold storage warehouse is the ratio of the actual volume of fruits and vegetables to the effective volume of the warehouse. The volume utilization rate of micro-cold storage is generally not less than 0.3, and of course it cannot be too high, otherwise it will be difficult to cool down. When the volume of the fruits and vegetables to be stored varies greatly, it should be divided into two or more cold storage rooms. In addition, a reasonable storage period should be selected, which is self-evident for the energy saving of the cold storage.
Ⅱ. Frequency conversion speed regulation technology is used for energy saving in cold storage. Since 80% of the power consumption of cold storage enterprises is the refrigeration system, and the power consumption of the compressor in the refrigeration system accounts for about 60%, the energy saving significance of the motor matched with the compressor is more important. for major. In the design of cold storage, the equipment is generally determined according to the maximum mechanical load condition that occurs throughout the year to meet the requirements of the peak heat load. However, in actual operation, due to the existence of food cold processing and other changing factors, the selected cold storage is often designed. The compressor runs for a short time at full load, and runs for a long time at low load, so that the compressor runs under the condition of less than the design load most of the time.
Ⅲ. Micro energy-saving cold storage Micro energy-saving cold storage is a storage facility with simple operation, reliable performance and good effect developed for the main management mode of agricultural production in my country and the economic and technical level of rural households. It has won the national patent and the eighth Special Gold Award at the China Patent New Technology and New Product Expo. It can be widely used in the storage and pre-cooling of agricultural and sideline products such as fruits, vegetables, grains, flowers, and medicinal materials, food, and fine chemical raw materials. important carrier. Refrigeration equipment is the most critical part of micro energy-saving cold storage, which is mainly suitable for rural households, wholesale markets, supermarkets, fresh-keeping refrigeration, quick-freezing and freezing.
Main features of micro energy-saving cold storage equipment:
(1) The refrigerant filling and debugging of the micro energy-saving cold storage have been strictly tested before leaving the factory. At the same time, the installation is convenient and fast. It only needs to connect the indoor unit and the outdoor unit with pipes and connect the power to work.
(2) The refrigeration unit of the micro energy-saving cold storage adopts imported fully enclosed refrigeration compressors, and the main control components can also use foreign products, so the operation is safe and reliable, and the trouble-free operation time is long. (3) The automatic control system of the miniature energy-saving cold storage adopts microcomputer control, the temperature control is accurate, and the operation is simple. Temperature inside the library.
(4) The unit of the micro energy-saving cold storage adopts hot air or electric heating defrosting method, the defrosting time is short, and the temperature fluctuation in the storage is small during the defrosting period. There are two most commonly used specifications for micro energy-saving cold storage: 90m3 and 120m3 volume. The construction investment is generally 15,000 to 20,000 yuan. The warehouse built according to the design points of the micro energy-saving cold storage has fast cooling speed, good thermal insulation performance, and small temperature fluctuation of the cold storage. Generally, within 48 hours after the empty warehouse is turned on, the temperature of the cold storage can be reduced from 20 °C to 0 °C; in the pre-cooling and cooling stage of the fruit, the daily power consumption of the equipment is generally 40~50 degrees, and the daily power consumption of the cold storage is only after the temperature of the cold storage is stable. 7~8 degrees, the northern region can use natural cold source ventilation to cool down in winter, and the monthly power consumption is very low.