Multiphase Flows

Multiphase Flows

Which drag coefficient is used by default for the calculation of the bubble detachment frequency within the Wall Boiling model?

    • FAQFAQ
      Participant

      The calculation of the bubble detachment frequency is based on the evaluation of the bubble rise (terminal) velocity by considering the balance between the buoyancy force and the drag force. To model the exerted drag force on the detaching nucleate bubble a drag coefficient is required. The RPI model uses a drag coefficient and not a factor which is set to unity. This is taken from the work of W.-C. B. Ceumern-Lindenstjerna, “Bubble departure diameter and release frequencies during nucleate pool boiling of water and aqueous NaCl solution,” in Heat Transfer in Boiling, E. Hahne and U. Grigull, Eds., Academic Press and Hemisphere, New York, NY, USA, 1977. This drag coefficient could be altered by the user to any user defined drag law (for example as expressions written Grace or Schiller-Naumann drag laws).