Cascade CO2 heat pump capable of achieving defrosting through reversing of four-way valve and defrosting method of cascade CO2 heat pump

Abstract

The invention discloses a cascade CO2 heat pump capable of achieving defrosting through reversing of a four-way valve and a defrosting method of the cascade CO2 heat pump, and belongs to heating cycle technologies of heat pumps. A conventional CO2 heat pump system cannot achieve defrosting through reversing of the four-way valve. The cascade CO2 heat pump is characterized in that a mature four-way valve reversing defrosting technology of a conventional refrigerant system is fully utilized, when a system detects that an air source evaporator needs to be defrosted, a second compressor is stopped, the CO2 heating cycle is stopped, a four-way valve of the conventional refrigerant system is controlled, the conventional refrigerant system absorbs heat from a user hot water demand side, and the frost condensed on the surface of an air source heat exchanger is removed. According to the cascade CO2 heat pump and the defrosting method, the defrosting time of a cascade CO2 system can be remarkably shortened, the defrosting efficiency of the system is improved, and a technical scheme is provided for reliable operation of the heat pump system at an extremely low environmental temperature.

Description

technical field [0001] The invention relates to heat pump heating cycle technology, in particular to the realization of a cascaded CO system operating at extremely low ambient temperature (below -15°C) with four-way valve reversing defrosting 2 Heat pump and cascade CO 2 Heat pump defrost method. Background technique [0002] Due to CO 2 It is one of the few natural refrigerants that has little damage to the environment. Therefore, based on its unique thermophysical properties, CO 2 Research on heat pump technology has become a hot topic in the refrigeration and air conditioning industry. Although there are many CO 2 The application of heat pump technology is listed, but limited by some technical conditions, there is still a long distance from extensive commercial use. The typical technical difficulty is CO 2 System defrost problem. Existing CO 2 The defrosting methods of the heat pump system, such as steam bypass, electric heating, etc., have low defrosting efficienc...

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved by the present invention is that existing CO 2 The heat pump system cannot defrost with four-way valve reversing and the defrosting methods such as steam bypass and electric heating are inefficient. A cascade CO defrosting with four-way valve reversing is provided. 2 Heat pump and cascade CO 2 Heat pump defrost method to ensure CO 2 Reliable operation of heat pump systems at very low ambient temperatures

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