Design Considerations for Duct-Type Electric Air Heaters


(1) Reasonably design the air volume and temperature rise. The power of the electric air heater is calculated based on the air volume and temperature rise. On the premise that the air volume and temperature rise meet the requirements, it is not advisable to use excessive air volume or excessive temperature rise, as this directly leads to excessive power of the heater and increases energy consumption. Excessive air volume and temperature rise are unnecessary. Comprehensive consideration and reasonable design are needed to determine appropriate parameters.



(2) The surface of the duct-type electric air heater should be insulated. Most power plants (owners) only insulate the pipeline at the outlet of the electric heater when using it, but do not insulate the surface of the heater itself. Comparative data show that adding insulation to the surface of the electric heater can reduce energy consumption by 5% to 10%. Over long-term operation, the energy savings are considerable. Power plants (owners) should add insulation to the electric air heater while insulating the pipeline.



(3) Reduce the pressure loss of the electric air heater itself. The air to be heated generates pressure loss when flowing through the electric air heater. The greater the pressure loss, the greater the energy consumption of the fan. Improvements and innovations should be made to the structure of the electric air heater itself to minimize the pressure loss.












Factors Affecting the Performance of Duct-Type Electric Air Heaters


  1. Increasing the gas inlet velocity of the electric air heater can enhance convective heat transfer and reduce the surface temperature of the heating elements inside the heater. This not only helps extend the service life of the heating elements but also reduces heat loss, thereby improving the efficiency of the air heater. However, if the velocity is too high, the pressure loss increases sharply, which is detrimental to heating efficiency.



  2. If other conditions remain unchanged, changing the surface load will cause the wall temperature of the heating elements in the electric air heater to change linearly. If the surface load increases, the wall temperature of the heating elements will increase, which reduces their service life. However, if the surface load is too small, the wall temperature is too low, and the efficiency of the air heater decreases. Therefore, the selection of the surface load of the heating elements in the air heater is relatively important.



3. When the final air temperature T2 in the air heater increases, the air viscosity increases and the Reynolds number decreases, leading to a reduction in convective heat transfer intensity. The surface temperature of the heating elements in the air heater rises simultaneously, increasing heat loss and thus reducing the efficiency of the heat exchanger. If T2 increases too much, the surface temperature of the heating elements will also rise significantly, making it unbearable for ordinary heating elements. Therefore, the increase of T2 is usually limited by the heat resistance of the heating element materials in the air heater.