The district heating system refers to the hot water system in the thermal power plant, regional boiler room or heat exchange station after the central heating of water, the heat in the state of hot water or steam through the municipal heating network to various buildings, residential areas, urban neighbourhoods or entire industrial enterprises. If the water quality of the urban heat network meets the water requirements, the water can also be directly drawn from the heat network when the conditions of the heat network permit. As shown in Fig. 1.1, the regional hot water supply system is suitable for cities and industrial enterprises with concentrated building layout and large hot water consumption, and is widely used in foreign countries, especially in developed countries. The district heating system mainly consists of four parts: heat source, heating network, user and heat exchange station.