ISSN On-line: 2688-7231
ISBN On-line: 978-1-56700-524-0
Proceedings of the 26thNational and 4th International ISHMT-ASTFE Heat and Mass Transfer Conference December 17-20, 2021, IIT Madras, Chennai-600036, Tamil Nadu, India
Enhancement of quenching heat transfer using extended surfaces.
Rapid cooling of materials has major industrial applications such as, metal forming, nuclear reactor safety, and increasing chill-down efficiency of cryogenic systems. Heat dissipation is severely restricted when the surface temperature of the material exceeds the minimum film boiling temperature due to the formation of a vapor layer. Incorporation of micro-scale surface modification has shown to reduce the duration of film boiling regime by enhancing the surface wettability and facilitating liquid-solid contact. In the present work we investigate the effect of macro-scale (fins) surface modifications on the quenching of vertical cylinders at different pool temperatures. We observe that the geometry of the fins plays a significant role in the vapor flow dynamics, influencing the heat transfer in the film, transition and nucleate boiling regimes. The use of annular fins is shown to reduce the quench duration by 3.8 times and increase the maximum heat flux by ~230% for a pool temperature of 25°C. At higher pool temperature, the heat dissipation from the annular finned samples is restricted due to the vapor entrapment; this drawback is overcome by using pin fins to allow the vapor generated to escape along the surface without the vapor bubbles getting trapped in the fin gap region. The vapor entrapment is shown to be mitigated by use of pin fins that result in a 2 times reduction in quench duration compared to the annular finned (FS-5) surface at a pool temperature of 80 °C.