Study On Defrosting Control Technology Of Air Cooled Refrigerator Of BCD-350W

The problem of frost and defrost restricts the development of large-capacity air-cooled refrigerator and energy level over a long period of time. On the one hand, frosting reduces the air flow area, which increases flow resistance and decreases the heat transfer; on the other hand, frosting increases the resistance of heat transfer between the fin surface of evaporator and air, which reduces the performance of refrigeration. Therefore, when the frost on the surface of fin of evaporator reaches a certain thickness, the working performance of the refrigerator decreased rapidly, which needs to defrost on time.Finding the reasonable breakthrough point and exit point of defrost is the key to defrosting control technology. At the present time, the air-cooled refrigerator generally uses the time-temperature method. But it can not reflect the changes of environment temperature and working conditions, easily leads to defrosting delay and defrosting not clean or too long defrosting time, which not only affects the food quality, but also increases the energy consumption of refrigerator. In order to improve the level of defrosting control technology, studying on the theory of frost and defrost, experiments and applications has important significance.Based on the time-temperature method, considering the characteristics of the evaporating temperature and the temperature of the freezing chamber, a new type of time-temperature difference method of defrosting control technology comes out, fruitful experiment research and engineering applications are carried out, and the following conclusions can be drawn:1) Based on summarizing the research on frosting and defrosting technology, the frost growth model and heat exchanger under frosting model are established. By the dynamic simulation research, that the regular pattern of frost thickness, density and heat transfer coefficient varying with the inlet air temperature, relative humidity, wind speed and spacing of fins can be preliminary mastered.2) Experiments of typical ambient temperature and heat and moisture load were carried out, parameters of internal temperature were measured when electric air door and box door was opening or closing. The experimental results shows that: the difference, named△T, between the evaporating temperature and the temperature of the refrigerating chamber becomes larger with the increase of accumulative time of compressor. The△T of the opening door of refrigerator is open is lower than that of the closure. The value of△T reduces with the increase of the environmental temperature. By the above regular pattern, a new kind of defrosting control technology is put forward based on the difference.3) Based on theoretical and experimental research, a new technique of defrosting control is designed and the experimental verification is carried out. The percentage of defrosting energy consumption in total energy consumption is less than5%, which meets the design requirement.the experiment results indicate that the defrosting control technology is reliable and adaptable.