The energy saving of household refrigerators is only an effective way to solve problems by optimizing the refrigeration system, improving the structure and design of the products, rationally using materials and advanced control methods.
1 refrigeration system energy saving
1.1 Production and use of high efficiency compressors
The compressor is the "heart" of the refrigeration system. Its variety and quality directly affect the various performances of the refrigerator, which plays a decisive role in the energy consumption of the whole refrigerator. Therefore, the development, production and adoption of high-efficiency compressors are the key to energy saving of the refrigerator. Rotary compressors have the advantages of high volumetric efficiency, stable operation, and low noise, and their efficiency is about 10% higher than that of piston compressors. The RG series high-efficiency R134a compressor produced by American Meili Refrigeration Co., Ltd. has a COP value of about 115 (the general compressor has a COP of about 111), while its RH series ultra-efficient R134a compressor has a higher COP value. About 116.
A refrigerator using such a compressor has the advantages of high cooling efficiency and low power consumption. China Kelon Company adopts the alternative of cyclopentane + isobutane. The energy consumption of the refrigerator is 35% higher than that of China's current Class A energy consumption without thickening the insulation layer of the refrigerator. In addition to the optimization of the refrigeration system and carbon In addition to the energy-saving effect of the hydrogen refrigerant itself, the main reason is the use of Danfoss' high-efficiency compressor.
Therefore, the production and adoption of high-efficiency compressors is a powerful measure to save energy.
1.2Select the best refrigerant charge
Refrigerator refrigerant charge is one of the key factors affecting refrigeration performance. Too much or too little charge is unfavorable to the system, and the performance of the corresponding refrigerator is different. Only by ensuring the optimal charge of the refrigerant, the energy consumption of the system can be minimized. Through the combination of computer dynamic simulation and experiment, the optimal charging amount of refrigerant can be accurately determined, and the advanced charging system can be used to ensure the refrigerant charging accuracy of the refrigerator system, thereby achieving the goal of low energy consumption.
1.3 Optimize the pipeline direction of the system
When designing the refrigeration system of the refrigerator, the first problem is the orientation of the system pipeline. The arrangement and orientation of the anti-condensation pipe is a direction that affects the energy saving of the refrigerator. Most refrigerator manufacturers use the superheated gas discharged from the compressor to heat the door frame to raise the temperature of the door frame to prevent condensation. However, due to the high temperature of the superheated gas and the large temperature difference between the refrigerator and the refrigerator, the leakage heat in the tank is increased, which is disadvantageous for reducing the energy consumption, and at the same time increases the temperature non-uniformity in the tank.
The split condenser is used to place the anti-condensation pipe between the left and right condensers, and the door frame is appropriately heated by the saturated section in the condenser, which not only has the effect of preventing condensation, but also reduces leakage to the refrigerator body. Heat has reached the goal of energy saving.
1.4 Adopt high efficiency circulation system
The freezer compartment and the refrigerating room temperature of the refrigerator are very different, while the cooling capacity of the traditional refrigerator freezer compartment and the refrigerating compartment is provided by an evaporator. The evaporation temperature is determined by the temperature of the freezer compartment, and the difference from the condensation temperature is large. The principle shows that the greater the temperature difference, the greater the irreversible loss of the thermodynamic cycle and the lower the efficiency of the refrigeration cycle. If a double evaporator circulation system is used, the two evaporators provide cooling capacity to the freezing compartment and the refrigerating compartment respectively, thereby reducing the irreversible loss of the system and improving the refrigeration cycle efficiency.
1.5 Looking for an efficient defrosting method
The ideal defrosting method for the refrigerator evaporator is to defrost according to the thickness of the frost layer on the surface of the evaporator or the decrease in the heat exchange performance of the evaporator, but it is difficult to control and has not been realized in the product. At present, most of the frost-free refrigerators use the defrosting timer to control the electric heating wire defrosting. This method is simple and easy, but the electric heating wire needs to consume electric energy, and after defrosting, the temperature of the evaporator and its surrounding air rises. Causes greater energy consumption. Therefore, finding an efficient defrosting method is also an aspect of energy saving. At present, it is envisaged to use the newly developed bistable solenoid valve (the valve itself does not consume electricity) to control the high temperature exhaust of the compressor instead of the electric heating wire defrosting, improve the defrosting efficiency and save energy.
1.6 heat exchanger energy-saving design
The heat exchanger includes two parts, an evaporator and a condenser. For the evaporator, the increase of the refrigerant flow resistance causes the evaporation temperature to decrease, the system energy consumption increases, and the efficiency decreases. The evaporation coil with a large inner diameter can reduce the flow resistance and improve the efficiency; the heat transfer area of ​​the evaporator is increased. To ensure the required cooling capacity in the tank, the evaporation temperature can be appropriately increased, and the increase of the evaporation temperature is essential for reducing the energy consumption of the refrigerator; the high-efficiency heat exchanger is used to enhance the heat exchange effect of the condenser and reduce the condensing pressure. Effectively improve the efficiency of the system.
1.7 Energy-saving design of return air heat exchanger
The purpose of providing a return air heat exchanger in the refrigerator system is to supercool the refrigerant liquid in the capillary tube, thereby improving the cooling efficiency and reducing the energy consumption. In order to improve the heat exchange effect of the gas return heat exchanger, the capillary and the return gas pipe are arranged in a countercurrent manner, or the heat exchange length between the capillary tube and the return gas pipe is appropriately increased to enhance the heat exchange between the two, or the capillary tube and the return gas pipe are used for tin. The solder and soldering method is used to improve the heat transfer efficiency between the two. Computer simulations show that the heat transfer efficiency of this method is higher than that of the capillary passing through the return pipe.
Variable capacity means that energy-saving partitions are installed in the freezer compartment of the refrigerator, and the volume can be adjusted according to the number of frozen foods to achieve energy-saving purposes, and energy saving can be 10% to 40%. In addition, separate switches can be set for the freezing and refrigerating space. According to the number and requirements of the stored food, the two rooms can be used at the same time or one of them can be deactivated. When the food is small, the freezer is converted into a small refrigerating room, thereby achieving high efficiency. Use the refrigerator energy-saving.
2 box and door energy saving
As the refrigerator blowing agent CFC211 is switched to HCFC2 141b or cyclopentane, how to ensure the thermal insulation performance of the alternative blowing agent is better than CFC211 foaming agent is one of the problems that all countries are studying. The advanced micro-porous foaming technology can reduce the thermal conductivity of the insulation foam of the cabinet and the door body, and ensure the uniformity of foaming compactness at each position from the process, reduce leakage heat and reduce energy consumption; adopt vacuum insulation board technology (VIP technology for short) Foaming, its thermal insulation performance is about double that of the ordinary rigid polyurethane foam layer. It does not use Freon, protects the environment and saves energy.
The refrigerator door adopts integral foaming technology to avoid screw connection, which not only increases the strength and life of the door, but also reduces the external heat leakage. In addition, it is also possible to improve the sealing performance and reduce the energy consumption by changing the structure of the seal.
3 control system energy saving
3.1 Using variable frequency control
The frequency conversion control automatically adjusts the speed of the compressor motor according to the height of the refrigerator load, so that the cooling capacity provided by the compressor is always in the best match with the thermal load of the system. When the food to be placed needs to be frozen or ice-making, the compressor provides more cooling at high speed; when no one opens at night or during the day, the speed of the compressor decreases, and the ultra-static energy-saving operation state is entered. The whole process is automatically controlled by the frequency converter, which can improve the refrigeration efficiency of the refrigerator, save energy and reduce noise. For example, MR2J F48D refrigerator manufactured by Mitsubishi Electric Corporation of Japan, after inverter control, its power consumption has dropped from the previous 75kWh/month to the current 52kWh/month, saving 31%. The cost increased by using the inverter is less than one. Years can be recovered from the saved electricity bill.
3.2 Using neuron fuzzy control
Fuzzy logic control is mainly based on the temperature sensor to measure the temperature value of each room and the calculated temperature change, using fuzzy neural reasoning to determine the temperature of the food, and sometimes control the operation of the compressor, fan operation and damper opening and closing, to achieve the best operating state and The best preservation effect. The neural network is preset in the IC control program by continuously learning and memorizing the user's adjustment requirements, ambient temperature, number of door opening, food intake, etc., and then automatically selects the optimal control scheme to adapt to the user through the "expert" system. need. Use neuron fuzzy control to control the optimal defrosting time, reasonably distribute the cooling capacity of each box, pre-cooling when the refrigerator is used frequently (such as before cooking), weak operation when the ambient temperature is low, etc. In the best working condition, it can save energy, reduce noise, improve the quality of food frozen and preserved.
3.3 Control system energy-saving design
Since the compressor has a large power and consumes a lot of energy when starting, the frequent start and stop of the compressor is unfavorable for the energy saving of the system. Through the combination of computer dynamic simulation and experiment, the correct selection of the compressor's cooling capacity, start-stop ratio, duty cycle and control parameters can realize the energy-saving design of the control system. In addition, capillary throttling is used in the refrigerator. When the compressor is stopped, the high-pressure refrigerant flows to the low-pressure side until the system pressure reaches equilibrium. When the compressor is started again to establish a normal pressure difference, more energy is consumed. The control system of the differential pressure valve can maintain the pressure distribution state of the refrigerant before the compressor is stopped by controlling the on/off of the valve of the differential pressure valve, and reduce the energy loss from the next startup to the stable operation of the refrigeration system. For example, Mitsubishi's 300-litre refrigerators are equipped with differential pressure valves, which can save 5% to 10% after use.
4 development trend of household refrigerators
With the development and popularization of household refrigerators, the proportion of electricity consumption in total electricity consumption is increasing (13% in the US). Therefore, the energy efficiency of refrigerators is increased, and the home appliances in China are increasing. The competitiveness of the company, in line with the international level, has become an important task for production companies. In order to encourage enterprises to produce energy-efficient refrigerators and users to purchase energy-efficient refrigerators, countries around the world have adopted a series of policy measures. For example, the United States enacted the Energy Law, which has set energy consumption limits for twelve household appliances, including refrigerators; Japan has implemented energy-saving standards for household appliances; Europe has implemented energy efficiency standards for refrigerators; in addition, Canada, Australia, and Taiwan. The energy efficiency standards for refrigerators have also been formulated or implemented in countries and regions such as Hong Kong. China's household appliances energy-saving technology is also one of the key technologies in the "Ninth Five-Year Plan for National Key Technology Development", and the State Economic and Trade Commission has officially determined that during the "Ninth Five-Year Plan" period, the development of energy-saving and CFC s alternative technologies will be used as household appliances. The industry participates in international competition and catches up with key projects at the international level. Energy conservation has become a major issue of global concern. However, due to the late development of China's refrigerator industry, the development and application of refrigerator energy-saving technology has a big gap compared with developed countries. Therefore, we must strengthen technical exchanges with developed countries, and learn from foreign advanced energy-saving experiences and measures to promote China. The development of energy-saving work in refrigerators. At the same time, the government departments adopted a tilting policy to encourage enterprises to carry out technological innovation, vigorously carry out energy-saving product certification work, and promote the rapid development of refrigerator energy-saving technologies.
In short, in today's increasingly fierce competition in the home appliance market, how to take the lead in energy-saving, frequency conversion and Other technologies to enhance the high-tech content of products to occupy the market, thus guiding the upgrading of home appliances, has become the frontier of competition in the home appliance industry. Energy conservation is the development trend of home appliances in the world.
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