In the central heating system, the circulating water in the pipes is mainly tap water and deep well water, which are hard water. When water reaches boiling point, it creates sediment in the pipes. Due to the smaller flow channel of the plate heat exchanger, the flow velocity between the plates is also lower. The sediment is easy to form scale on the hot side or suspend in the circulating water, and then deposit on the surface of the heat exchanger to form secondary scale, which will affect the water quality and cause scaling and blockage of the heat exchanger.

The low thermal conductivity of the fouling layer greatly increases the heat transfer resistance and reduces the heat transfer efficiency of the heat exchanger to a certain extent. When a fouling layer is formed on the surface of the plate heat exchanger, it will reduce the flow area of the equipment and increase the resistance of the fluid flowing through the equipment. In turn, more pump power needs to be consumed, resulting in unnecessary cost waste.

Although the plates of the plate heat exchanger are made of stainless steel and have strong corrosion resistance, if the chloride ion content in the water is high, it will cause corrosion. Water and oxygen are also necessary conditions for heat exchanger plates to be corroded. In addition, due to corrosion, the metal materials of the heating system will be damaged, resulting in serious festering and leakage of pipes and terminal equipment. In addition, it will damage the room decoration materials, and in severe cases, the plate heat exchanger and boiler will be scrapped in advance. Therefore, the water quality index of the circulating water of the plate heat exchanger is very important.