Air source heat pump unit adopting double evaporators to alternately perform defrosting and defrosting method thereof

Abstract

The invention discloses an air source heat pump unit adopting double evaporators to alternately perform defrosting and a defrosting method thereof. Two air-cooled evaporators in parallel connection are arranged in an air source heat pump system; when one air-cooled evaporator frosts and enters the defrosting mode, the evaporator requiring to be defrosted is switched into a subcooler through function switch of a four-way reversing valve and a throttle mechanism in the air source heat pump system, a frost layer on the surface of the evaporator requiring to be defrosted is molten and removed through a high-pressure high-temperature liquid refrigerant at an outlet of a condenser in the air source heat pump system, and the defrosting purpose is achieved; and the other air-cooled evaporator absorbs heat from the environment, and continuous heating is achieved. The air source heat pump unit has the advantage that the direction of the refrigerant does not change during the defrosting process, reliability is relatively high, heating is continuously carried out during the defrosting process, comfort during the utilization process is improved, energy consumption during the defrosting process of the heat pump unit almost can be neglected, and defrosting efficiency is greatly improved.

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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