A double evaporator alternate defrosting air source heat pump unit and its defrosting method

Abstract

The invention discloses a double evaporator alternately defrosting air source heat pump unit and a defrosting method thereof. Two parallel air-cooled evaporators are arranged in the air source heat pump system. When one of the air-cooled evaporators is frosted and When entering the defrosting mode, through the function switching of the four-way reversing valve and the throttling mechanism in the air source heat pump system, the evaporator that needs to be defrosted is switched to a subcooler, and the condenser in the air source heat pump system is used to The outlet high-pressure and high-temperature liquid refrigerant melts and removes the frost layer on the surface of the evaporator that needs to be defrosted to achieve the purpose of defrosting; the other air-cooled evaporator absorbs heat from the environment to achieve continuous heating. The invention has the advantage that the refrigerant does not change direction during the defrosting process, and has high reliability; at the same time, the heating continues during the defrosting process, which improves the comfort during use; and the energy consumption of the heat pump unit during the defrosting process is almost Can be ignored, greatly improving the defrosting efficiency.

Description

technical field [0001] The invention belongs to the technical fields of refrigeration, air conditioning and heat pumps, in particular to an air source heat pump unit with double evaporators alternately defrosting and a defrosting method thereof. Background technique [0002] In areas such as the middle and lower reaches of the Yangtze River in my country, when the air source heat pump operates under low outdoor conditions, when the surface temperature of the outdoor heat exchanger is lower than the dew point temperature of the surrounding air and lower than 0°C, it will cause frost on the surface of the heat exchanger. Thaw regularly. Frosting on the surface of the evaporator will bring many problems to the unit. First, it will increase the heat transfer resistance of the outdoor heat exchanger and reduce the area of ​​the air circulation channel, which will lead to a decrease in the ventilation volume of the outdoor heat exchanger, and finally lead to a decrease in the heati...

AI Technical Summary

Problems solved by technology

But there are also some problems. For example, the phase change material used for thermal storage defrosting needs to be better matched with the heat required for defrosting, while hot gas bypass defrosting and return gas heating defrosting need to be set in the system. The gas-liquid separator with larger capacity indirectly increases the cost of defrosting

Moreover, these methods can only ensure that the indoor heat exchanger does not absorb heat from the room during defrosting, but cannot ensure that the condenser is still heating during defrosting.

In recent years, some experts and scholars have proposed to use two sets of evaporators to alternately defrost the unit, which greatly improves the defrosting efficiency, but the complexity of design, manufacture and control makes it difficult to popularize this technology on a large scale (Li Shusong. Alternate diversion of defrosting air Source heat pump system. Publication number: CN203413881U); In addition, when the two evaporators defrost alternately, it is necessary to adjust the energy of the compressor load to adapt to the evaporator load. If there is no reliable energy adjustment means, it will easily lead to low evaporation pressure and affect the entire heat pump. System (Huang Dexiang, Zhou Zhihui, Dai Jinping. A double evaporator air source heat pump. Publication number: CN204202231U)

[0004] To sum up, due to many technical and cost problems, the current air source heat pump defrosting method is still almost a four-way reversing valve reversing defrosting method, it is difficult to ensure uninterrupted heating during defrosting, and it is impossible to achieve defrosting. During frost, the indoor temperature or the temperature of the heated hot water remains stable and does not drop significantly, and the defrosting efficiency is low and energy consumption is large under extreme weather conditions, which seriously affects the comfort of use

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