Materials for high temperature heat exchanger applications: A review

Advanced super critical power generation units need handling of steam at around 750oC to increase the efficiency of unit. Power generation units are using ferritic steel (9 cr-1 Mo steel) but it cannot withstand very high temperatures and pressures. Ni based super alloy is one material that is better suitable for this purpose. The available super alloys can withstand high temperatures but rate of corrosion is also very high and will reduce the life of the steam transporting tubes. This means frequent breakdown of the plant and replacement of tubes is needed. The paper provides an insight on factors affecting the selection of heat exchanger tube materials especially those used in power generation units. It further emphasizes on the importance of continued research in high temperature heat exchanger materials in order to maximize reliability and minimize cost by upgrading the existing materials by slight additions of alloying elements or innovating new materials. Criteria for material selection, factors affecting the performance of heat exchangers and materials used for high temperature heat exchangers are discussed.