The characteristics and working principle of hot water boiler

The characteristics and working principle of hot water boiler

Due to its small size, high thermal efficiency, simple and reliable system, stable operation and high safety, the vacuum hot water boiler has been used more and more in engineering projects. In a project design, a double-circuit vacuum hot water boiler is used to provide 60°C-50°C air-conditioning hot water and 65°C-5°C sanitary hot water. After the design project is used in two winters, the owner thinks that the operation is convenient. No need for professional age to manage boiler operation, the unit has high thermal efficiency, sensitive temperature control, convenient load adjustment, and can meet the load requirements in a short time after starting up:

First, the working principle of vacuum hot water boiler:

Vacuum hot water boilers have appeared in the 1970s, and the first finished machine was introduced in Japan. In the late 1980s, some manufacturers developed vacuum hot water boilers, but they have not been promoted due to technical problems. Nowadays, this type of machine that has been relatively mature in Japan has also been produced in a joint venture factory in China. The author chose the double-circuit vacuum hot water boiler of the factory.

The structure of the vacuum hot water boiler is shown in Fig. (1), which is composed of a combustion chamber (furnace), a water pipe, a vacuum chamber, a heat exchanger, and a heat medium water. The inside of the body is in a vacuum state and is isolated from the outside air to form a sealed state. The heat medium water covers the furnace and the water pipe and is sealed inside the body. The pressure in the negative pressure steam chamber is kept at atmospheric pressure. When the heat medium water enclosed therein is heated by combustion, it immediately boils and generates heat and water. Steam at the same temperature. During the ascending process, the steam generated in the machine contacts the surface of the heat exchanger disposed in the negative pressure steam chamber. Since the water temperature in the heat exchanger is lower than the steam temperature, the steam will condense on the surface of the heat exchanger and release a large amount of heat of vaporization. The water in the heat exchanger is heated, and the condensed water is returned to the heat medium water under the action of the strategy. Therefore, the heat medium water continuously performs a cycle of "boiling = evaporation = condensation = heat medium water" in the closed body. There is no need to replenish condensate or risk of empty burning. The water in the heat exchanger is heated and delivered to the user for air conditioning and sanitary hot water.

In order to ensure the reliability of the operation of the vacuum hot water boiler, the manufacturer must guarantee in three aspects:

1. In order to ensure the vacuum inside the boiler, it is subject to strict inspection during the production of the factory, and the gas is used for leak detection to ensure the tightness of the boiler body during the production process. In order to maintain the degree of vacuum, and in order to prevent the accident, the factory is equipped with a pump as a standard part. In the vacuum hot water boiler tank, when the heat medium water is heated to 90 ° C, the air pump automatically operates according to the vacuum degree in the tank body, and not only the air in the tank is extracted, but also the oxygen dissolved in the heat medium water is removed to keep it. A certain negative pressure, the tank will not corrode.

2. The heat medium water is a kind of clean water specially treated by the manufacturing factory for removing impurities, deoxidizing and softening. It can be used for one-time infusion in the production, and can be recycled during operation. Generally, there is no special case without filling. In the design and research, the author visited the factory user, a motor factory in Shanghai, a vacuum hot water boiler that was put into operation in 1987. It has been used for ten years without filling the superheated medium water, and still works normally.

3. The heat exchanger in the boiler has special requirements, and SUS444 stainless steel pipe is used. This pipe requires special process for processing. The pipe is not easy to scale, has high heat transfer efficiency, does not rust, and is superior to ordinary heat exchange tubes in terms of water quality and flow rate limitation.

Second, vacuum hot water boiler system features:

1. High safety: in the "Hot Water Boiler Safety Technical Supervision Regulations" (Lao Boiler Ning [1991] No. 8) issued in 1992, the hot water boiler room with the rated outlet hot water temperature lower than or equal to 95 °C is allowed. When the house is connected or located in the basement, semi-basement or first floor of a multi-storey building, and the capacity regulations (T-100) V5 of any boiler in the boiler room, the boiler room can be connected to the general civil building (T For the working temperature of the boiler, the temperature is °C, V is the boiler water capacity m3). Since the temperature of the hot water of the vacuum hot water boiler does not exceed 100 ° C, T-100 ≤ 0 ° C, can meet the safety requirements, and is selected for many projects.