Design and comparison of the sealing system for two types of air preheaters

Air preheaters are used to recover the waste thermal energy of hot flue gasses for preheating the inlet air of thermal equipment. Leakage is one of the most important issues in air preheaters due to its negative effect on overall thermal efficiency. In this study, two types of air preheaters have been designed to recover the low-grade waste heat. Also, a suitable sealing system was designed for both of them. To design seals, rotary rubber seals, thin shim plates and flexible fireproof corks have been studied. The air preheaters have been compared from economic and technological aspects. Finally, the best air preheater was manufactured. The manufactured air preheater has been optimized based on Taguchi Qualification Method and the best levels of geometrical and operational parameters were determined. According to the results, the flexible fireproof cork has a positive effect on leak sealing under low-grade temperature. The air preheater increased the temperature of the inlet compressed air up to about ۳ times and recovered ۳۱% of waste thermal energy. The use of new methods to design and manufacturing suitable seals for rotary air preheaters to enhance the overall thermal efficiency is recommended.

Keywords:

Heat exchanger , Leakage , Ljungstrom , Waste heat recovery