The intermediate medium used to transfer heat in urban central heating systems, also known as heating medium or heating element. The widely used heating medium in modern thermal processes is water, because water exists in large quantities in nature, has a large heat capacity, and can circulate economically and effectively in the heat exchange process. Urban centralized heating systems also commonly use water as the heating medium, in the form of hot water or steam, carrying heat from the heat source and delivering it to users through the heating network. The hot water heating system is driven by a water pump for circulation, with a water flow rate of about 1-2 meters per second and a conveying radius of over 10 kilometers. The supply and return water temperature is determined based on technical and economic comparisons.