Air Preheater Effectiveness Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026How close to the theoretical maximum a preheater actually gets
Effectiveness compares the heat a preheater actually recovers against the maximum theoretically possible if the incoming air could be heated all the way up to the hot gas inlet temperature - a real-world performance benchmark, not just a raw temperature rise number.
Worked example
For air heated from 25C to 250C using hot gas entering at 400C:
Effectiveness = ((250 - 25) / (400 - 25)) x 100 = 60.0% effectiveness
Real air preheaters typically achieve 60-85% effectiveness in practice - reaching 100% would require infinite heat transfer surface area, since heat exchange rate naturally slows as the temperature difference between the two streams shrinks toward zero.