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It should be pointed out that the evaporator of the variable temperature chamber is matched with the evaporator of the freezer and freezer according to the requirements of three-star freezer (-18℃), and the refrigerant charging amount is also charged according to the refrigeration capacity of the variable temperature chamber used in the freezer. In this way, by controlling the bistable electromagnetic valve through temperature setting, the variable temperature chamber can be used as a freezer or a soft freezer (-7 ~- 10℃) or a freezer or closed. Table 1 is the measured data of energy consumption. It can be seen that increasing the temperature of the variable temperature chamber alone (using the variable temperature chamber as a soft freezing chamber or a refrigerating chamber) can save energy, and closing the variable temperature chamber alone is more energy-saving.
Optimal matching of refrigeration system and energy-saving design of pipeline direction
5. 1 Optimal matching of refrigeration system
This project comprehensively considers the relevant parameters such as box heat load, system refrigeration capacity, compressor efficiency and refrigerator working cycle. , so as to achieve the best matching state.
5. 1. 1 The climate type in the design should match the climate in the use area, otherwise, the power consumption will increase, or even there will be non-stop phenomenon. At the same time, the heat load matching relationship between freezer and freezer will be determined according to the climate type of the product (subtropical design in project development). In product design and prototype test, the relevant parameters of the system loop are repeatedly adjusted to achieve the best energy-saving matching relationship between refrigeration and refrigeration, evaporator and condenser, compressor exhaust and evaporator evaporation capacity, capillary throttling and evaporation temperature. Table 2 shows the key state points of the system that must be controlled in the adjustment process and the corresponding adjustment measures [5].
5. 1.2 When designing a refrigerator system, the selection of working time coefficient is very important. If the working time of the compressor is too short and the compressor starts frequently, the energy consumption will increase because of the high starting power; If the working time is too long, the compressor always works at a lower evaporation temperature, the working efficiency of the compressor is too low, and the energy consumption will also rise. When selecting the compressor, the maximum heat load requirement of the refrigerator should be met, and the smaller compressor should be selected as far as possible under the load requirement. In the project development, a high-efficiency compressor with a power of 90W was selected. It is determined that the working time coefficient of the refrigerator is appropriate and the energy consumption is less, as shown in Table 1.
5. The optimal matching of1.3 refrigeration system also includes the matching of refrigerant consumption in the refrigeration system. Too much or too little refrigerant will affect the refrigeration effect of the refrigeration system, leading to an increase in power consumption. Therefore, after the performance of the system is determined by its structure, it is necessary to carry out matching test on its refrigerant consumption. In the project development, the charging amount test is different from the ordinary refrigerator, and a high-precision charging system is adopted to ensure the best charging amount, so that the system can work efficiently and achieve the purpose of saving energy and reducing consumption.
5. 1.4 It is an important issue to improve the throttling system and correctly select the capillary length and diameter to determine the optimal capillary flow, which is closely related to the optimal matching of evaporator and condenser. If the length of capillary tube is long or the diameter of capillary tube is small, there will be a large pressure difference when throttling, and the refrigerant flow will be small, the evaporation temperature will be low, and the compressor exhaust volume will be small, which will reduce the refrigeration capacity of refrigeration system. In the design, the initial theoretical calculation is often only instructive, and it must be determined after many tests and debugging. During the project debugging, temperature-sensing thermocouples are distributed at the main state parameter points of the main components of the refrigeration system, and pressure gauges are installed at the high and low pressure ends of the compressor. Through the test curves and data of various working conditions, with the help of pressure enthalpy diagram, the best refrigeration cycle working conditions are found, and the best flow rate and filling amount are determined.
5.2 Energy-saving design of refrigeration system pipeline direction
5.2. 1 Energy-saving design of anti-condensation pipe is introduced in 3.4.
5.2.2 Energy-saving design of return air heat exchanger. Environmental protection refrigerants such as R600a, R 134a are adopted. For example, R 12, setting return air heat exchanger in the system and adopting regenerative cycle are effective measures to improve refrigeration coefficient and refrigeration capacity per unit volume.
The heat exchange efficiency is enhanced from the following three aspects: (1) Refrigerant in capillary and return pipe adopts countercurrent heat exchange; (2) parallel welding (or thermoplastic process) is adopted for the capillary and the air return pipe; (3) As far as possible, increase the welding length between the capillary tube and the air return pipe to make the final heat exchange efficiency reach 98%, which can obviously improve the refrigeration capacity of the system.
5.2.3 Reasonable arrangement of refrigerant pipes in two heat exchange equipment (evaporator and condenser). The improvement of heat exchange capacity of the two heat exchange equipment is very important to improve the refrigeration capacity of the system and reduce energy consumption, and the improvement of heat exchange capacity is closely related to the reasonable arrangement of refrigerant pipelines. In the development of the project, the double rows of parallel coils of the evaporator in the refrigerator are attached to the inner container, and the evaporator in the freezer adopts a layered three-dimensional structure. The condenser is designed as a mixed arrangement of horizontal and vertical coils and hung externally. Through these measures, the heat exchange capacity between evaporator and condenser is greatly enhanced. According to the actual measurement, the maximum daily power consumption of the refrigerator is only 0.39 degrees, while the power consumption is below 0.35 degrees in the energy-saving state.
5.2.4 Pay attention to reducing the noise of the refrigerator in the energy-saving design of the refrigeration system pipeline, so as to ensure the energy-saving of the refrigerator and control the noise within a reasonable range.
6 conclusion
By improving the structure of heat exchanger, adopting the design of multi-layer composite three-dimensional evaporator, changing the single vertical row tube into the horizontal and vertical mixed wire tube external condenser, with the help of the optimal matching of refrigerator compressor, condenser, evaporator and capillary tube, and the optimal design of variable temperature control technology, the BCD- 186CHS direct-cooling refrigerator has a maximum daily power consumption of 0.39 degrees, but it is in an energy-saving state. Compared with the direct-cooling refrigerator with the same size and fixed freezing chamber volume, the refrigerator developed by this project not only meets the various needs of consumers for temperature zones, but also significantly saves energy and reduces consumption.
refer to
1 dialect. The general trend of refrigerator market demand. Household appliance technology, 2002, (7): 34 ~ 35
2 www . clasp online . org/download/General/200 1/2 1 1/The-SL-guide book . pdf
Refrigerator evaporator of Henan Xinfei Electric Appliance Co., Ltd.. China, utility model, 2004200 1092 1.8, May 3, 20041.
4 Li Gang. An energy-saving direct-cooling refrigerator with soft freezer. China Zhang, utility model, 20042001137.9.25.2004.
5 Zhao Xianmei. Research and development of energy-saving BCD-248/H and BCD-2 18/H refrigerators. Journal of Refrigeration, 2002, 1: 6 1 ~ 65.