Before revision: Rotating-plate regenerative air preheater 325px|Typical Rotating-plate Regenerative Air Preheater (Bi-sector type)Course SI:428A Online publication of the U.S. Environmental Protection Agency's Air Pollution Training Institute, known as APTI (Scroll down to page 23 of 28) 325px|Principle function for the Fredrik Ljungström regenerative preheater.
After revision: Rotating-plate 's Ljungström regenerative air air preheater 325px|Typical Rotating-plate Regenerative Air Preheater (Bi-sector type)Course SI:428A Online publication of U.S. Environmental Protection Agency's Air Pollution Training Institute, known as APTI (Scroll down to page 23 of 28) 325px|Principle function for the Fredrik Ljungström regenerative preheater.