Air duct heater reasonably depicts air volume and temperature rise

The power of the electric air heater is determined based on the calculation of the air volume and temperature rise. Under the premise that the air volume and temperature rise have met the demand, it is not appropriate to use excessive air volume and temperature rise. The power of the heater is too large, increasing energy consumption. Excessive air volume and temperature rise are not necessary. To sum up consideration, reasonably describe, determine the appropriate parameters.