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. Under the premise that the air volume and temperature rise meet the requirements, excessively large air volume and temperature rise should not be used, as they directly lead to excessive heater power and increased energy consumption. Excessive air volume and temperature rise are unnecessary. Comprehensive consideration should be given to reasonably design and 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, without any insulation treatment on the surface of the heater itself. Comparative data show that adding an insulation layer on 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, which 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 will reduce the service life of the heating elements. However, if the surface load is too low, the wall temperature is too low, and the efficiency of the air heater heat exchanger 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, due to the increase in air viscosity, the Reynolds number of the gas decreases, which reduces the 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. When 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 in T2 is usually limited by the heat resistance of the heating element material in the air heater.