BT-2 Pressure Drop in Vertical Tubeside Boiling

J. W. Palen, C. C. Shih, and J. Taborek

New HTRI methods are presented for pressure drop in vertical tubeside boiling with upward flow. All boiling flow regimes are considered. Except for mist flow, the correlations are based on the Martinelli separated flow model but contain the following important adjustments found necessary for good predictions over the extremely wide range of conditions covered by the HTRI data:

  • A tendency of the original Martinelli correlation to predict high at high pressure and low at low pressure was corrected by including additional physical property parameters.
  • The unsafe (low) prediction of static head in vacuum by the Martinelli volume fraction correlation was corrected by switching to a modified form of the Levy correlation at low pressure. This greatly improved prediction of both circulation rate and heat transfer for vacuum reboilers.
  • Pressure drop in film boiling was greatly overpredicted by all previous correlations, and a modification of the separated flow model was made to produce a new correlation for this regime.
  • The homogeneous model was found to give adequate results for the mist flow regime.

The correlations were based on over 500 HTRI data runs taken on three vertical thermosiphon reboiler bundles which are described in HTRI Report BT-1. The data included a much wider range of operating pressure than has been previously covered in an experiment of this type. Reduced pressures ranged from 0.0023 to 0.9. A number of different types of fluids were also covered as listed in HTRI Report BT-1.