A hydrodynamic critical heat flux model for saturated pool boiling on a downward facing curved heating surface

✍ Scribed by F.B. Cheung; K.H. Haddad

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 1001 KB
• Volume: 40
• Category: Article
• ISSN: 0017-9310
• DOI: 10.1016/s0017-9310(96)00208-6

✦ Synopsis

A theoretical model is developed to predict the critical heat flux (CHF) limit for saturated pool boiling on the outer surface of a heated hemispherical vessel. The model considers the existence of a microlayer underneath an elongated vapor slug on a downward facing curved heating surface. The micro-layer is treated as a thin liquid film with numerous micro-vapor jets penetrating it. The micro-jets have the characteristic size dictated by Helmholtz instability. Local dryout is considered to occur when the supply of fresh liquid from the two-phase boundary layer to the micro-layer is not sufficient to prevent depletion of the liquid film by boiling. A boundary layer analysis, treating the two-phase motion as an external buoyancy-driven flow, is performed to determine the liquid supply rate and thus the local critical heat flux. The model provides a clear physical explanation for the spatial variation of the CHF observed in experiments and for the weak dependence of the CHF data on the physical size of the vessel.