Thermal and flow characteristics of a cylindrical superheater with circular fins

Abstract

In the present study, a cylindrical superheater for producing high-temperature superheated steam was installed in a furnace, and its heat flow characteristics were investigated. The effect of applying circular fins of various curvature angles to the inside of the superheater was analyzed to improve heat transfer performance. The steam flowing into the cylindrical superheater showed a swirling flow along the wall surface as it fell down to the bottom of the superheater, and received heat from the high-temperature combustion gas. When the numerical analysis data was compared to experimental results for verification, the hot gas temperature and superheated steam temperature were found to be similar, within 5% and 8.3%, respectively. The temperature of the steam discharged through the superheater outlet was higher when fins were applied to the superheater, compared to the case without the fins, because the heat transfer area was increased and a secondary flow was generated between the fins. As a result, compared to the superheater without fins, the pressure drop increased by 2.2% with flat fins, 2.8% with 30 degrees fins, and 3.8% with 60 degrees fins. The discharge steam temperature increased by 0.5% with flat fins, 1.8% with 30 degrees fins, and 2.4% with 60 degrees fins. Also, Nusselt numbers increased by 19.6% for the flat fins, 20.3% at 30 degrees fins, and 21.5% at 60 degrees fins.