An air source heat pump is an energy-saving device that utilizes high-level energy to flow heat from a low-level heat source to a high-level heat source. As the low-level heat source of the heat pump, air is inexhaustible , available everywhere, and can be obtained free of charge. Moreover, the installation and use of air source heat pumps are relatively convenient. The current products include household heat pump air conditioners, commercial unit heat pump air conditioners and heat pump cold and hot water units. According to the capacity of the unit, it is divided into: household small unit, medium unit, large unit, etc. According to the unit combination form, it is divided into: integral unit (units consisting of one or several compressors sharing a water-side heat exchanger are called integral units) and modular units (units composed of several independent modules, called for modular units) . (1) The air source heat pump system integrates the cold and heat sources, and does not need to set up a special refrigeration room or boiler room. The unit can be placed on the roof or the ground at will, without occupying the effective use area of ​​the building, and the construction and installation are very simple. (2) The air source heat pump system has no cooling water system, no cooling water consumption, and no cooling water system power consumption. In addition, many cases of Legionella infection caused by cooling water pollution have been reported. From the perspective of safety and hygiene, considering the air source heat pump also has obvious advantages. (3) Since the air source heat pump system does not need a boiler, a corresponding boiler fuel supply system, a dust removal system and a flue gas discharge system, the system is safe and reliable, and does not pollute the environment. (4) The air source heat pump cooling (hot) water unit adopts a modular design, and there is no need to set up a standby unit. During the operation, the computer automatically controls the operation state of the unit to adjust the output power and the working environment. (5) The performance of the air source heat pump will change with the outdoor climate. (6) In places with low outdoor air temperature, auxiliary heaters are required due to insufficient heat supply in winter by the heat pump.(1) For areas with hot summers and cold winters: the climatic characteristics of areas with hot summers and cold winters are that the summers are sultry, the average regional temperature is 25-30°C, and the number of days when the annual average temperature is higher than 25°C is 40-100 days; the winters are wet and cold, and the average temperature 0-10℃, the number of days when the annual average temperature is less than 5℃ is 0-90 days. The daily range of temperature is small, the annual rainfall is large, and the sunshine is small. The climatic characteristics of these regions are very suitable for the application of air source heat pumps. (2) For January with an average temperature of 1-13°C, the number of days with an annual average temperature of less than 5°C is 0-90 days. Under such climatic conditions, in the past, general buildings were not equipped with heating equipment. However, in recent years, with the development of modern buildings and the advancement of a well-off living standard, people have higher and higher requirements for living and working building environments. Therefore, modern buildings and high-end apartments in these areas have also begun to install heating systems. Therefore, in this climatic condition, the selection of air source heat pump system is very suitable. (3) The traditional air source heat pump unit can operate safely and reliably when the outdoor air temperature is higher than -3℃. The regional climate is characterized by low temperature in winter, and the average temperature in January is -10-0℃, but in the heating period, the time when the temperature is higher than -3℃ accounts for a large proportion, and the time when the temperature is lower than -3℃ Most of them appear at night. Therefore, air source heat pumps are used in buildings that operate mainly during the day (such as office buildings, shopping malls, banks, etc.), and their operation is feasible and reliable. In addition, the climate in these areas is dry in winter, and the outdoor relative humidity in the coldest month is about 45%-65%. Therefore, the frosting phenomenon of air source heat pump is not too serious.