A simulation technique for predicting the thermal performance of rotary regenerative heat exchangers, in particular those used for heating the intake air to power station boilers, has been developed and verified by means of site measurements. Various geometries of both rotating-hood and rotating-matrix types of air heaters can be accommodated in the simulation model, including packings of corrugated steel plates of various specified profiles and any given thicknesses and lengths in the flow direction. Rotational speed, leakage, blockage, and non-uniform inlet flow distribution may be taken into account as input variables. The heat transfer and pressure drop correlations for the various plates considered, which also form part of the input data, were determined experimentally using a single-blow transient test facility, constructed as part of this research program. The effect of erosion of the plates by fly ash particles carried in the outlet flue gas on heat transfer performance is also considered, and experimental results show that erosion has little effect on the thermal performance (up to the point that structural integrity is about to be compromised), but also that the pressure drop is reduced.