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Overview of air heater theory

Author: Pv:859 Time:2021-01-30

Air heater is an electric heating equipment which mainly heats the gas flow. The heating element of air heater is stainless steel electric heating pipe. The inner cavity of the heater is equipped with multiple baffle plates (guide plates), which can guide the gas flow direction, extend the retention time of gas in the inner cavity, so as to make the gas fully heated, make the gas heated evenly and improve the heat exchange efficiency. The stainless steel heating pipe of the heating element of the air heater is made by installing the electric heating wire into the seamless steel pipe, and the gap part is filled with the magnesium oxide powder with good thermal conductivity and insulation. When the current passes through the high temperature resistance wire, the heat generated diffuses to the surface of the heating pipe through the crystalline magnesia powder, and then passes to the heated air to achieve the purpose of heating.

introduce

A lot of hot air is needed in the fusion process. The compressed air output by the air compressor is sent to the air heater for heating after dehumidification and filtration, and then to the assembly of the melt injection die head. Air heater is a pressure vessel, and it must resist oxidation of high temperature air. Therefore, stainless steel must be used as the material. The heating element of air heater is stainless steel electric heating pipe. The heater cavity is equipped with multiple baffles, which can extend the retention time of air in the heater cavity to improve the heat exchange efficiency. The heating time of the production line can be shortened by increasing the number of heating pipes and increasing the installed power of air heater. The temperature control accuracy of draft air heater is required by melt spraying process, and the temperature of draft air is required to be stable within ± 1 ℃.

working principle

The primary coil with more turns and one secondary coil with less turns are installed on the same core. The voltage ratio of input and output is equal to the ratio of coil turns, while the energy remains unchanged. Therefore, the secondary coil generates a large current at low voltage. For induction heater, bearing is a short circuit single turn secondary coil, which passes through high current under low AC voltage, thus generating a large amount of heat. The heater itself and yoke are kept at normal temperature. Because the heating method can sense current, the bearing will be magnetized. It is important to ensure that the bearing will be demagnetized in the future so that it will not absorb metal magnetic chips during operation. Fag induction heater has the function of automatic demagnetization.

It is used to generate eddy current in alternating magnetic field to make the metal heat, which is usually used in metal heat treatment. The principle is that when thick metal is in alternating magnetic field, it will generate current due to electromagnetic induction. When thick metal produces current, current will form spiral flow path inside metal, so that heat generated by current flow is absorbed by metal itself, which will cause metal to rise rapidly.

The high temperature resistance wire is evenly distributed in the seamless tube of high temperature resistant stainless steel. The crystalline magnesia powder with good thermal conductivity and insulation performance is filled in the gap. This structure is not only advanced, high heat efficiency, but also has even heating. When there is current passing through the high temperature resistance wire, the heat generated diffuses to the surface of the metal pipe through the crystalline magnesia powder, and then passes to the heated part Or to go in the air to achieve the purpose of heating.

The electric air heater is mainly used to heat the required air flow from the initial temperature to the required air temperature, up to 850 ℃. It has been widely used in aerospace, weapon industry, chemical industry and many other scientific research and production laboratories in Colleges and universities. It is especially suitable for automatic temperature control and large flow high temperature combined system and accessory test. The range of air electric heater is wide: it can be heated to any gas, and the hot air produced is dry without water, non-conductive, non combustion, no explosion, no chemical corrosion, no pollution, safe and reliable, and the heated space can be heated quickly (controllable).

Technical characteristics

1. It can make the air heated to a very high temperature, up to 450 ℃, and the shell temperature is only about 50 ℃.

2. High efficiency: up to 0.9.

3. The heating and cooling rate block can reach 10 ℃ /s, and the adjustment is fast and stable. It is suitable for automatic control because of the fact that the air temperature is not in advance and lag, which makes the temperature control drift uncertain.

4. Good mechanical properties: because its heating body is made of special alloy, it has better mechanical properties and strength than any heat generator under the impact of high pressure air flow. This is more advantageous for the system and accessory test which needs long time and continuous air heating.

5. It is durable and has a service life of up to decades when it does not violate the operation regulations.

6. The air is clean and small.

Heater application range

Air heater is a widely used heater. We call it air heater. In fact, it can be divided into many kinds according to the heating gas failure. The common ones are nitrogen heater and hydrogen heater. These can also be called pipe type gas heaters.

Maintenance and troubleshooting

maintain

The control part of air heater is precision instrument. It should be handled carefully during transportation, and it is strictly forbidden to impact or hit. The cylinder part shall be hoisted reasonably to avoid deformation and damage to the internal heating elements. Air heater and control cabinet are placed in the warehouse, and it is strictly prohibited to rain.

Troubleshooting

Fault 1: the digital display meter does not work.

Check whether the air switch is closed and the control circuit is in good condition.

Fault 2: heater temperature does not rise.

Check whether fuse is in good condition and air heater is damaged?

Fault 3: three phase unbalance.

(1) Check whether the three-phase incoming voltage is missing.

(2) Open the air heater cover and check the single electric heating element for open circuit with a multimeter.