BK1-1 Thermal Design of Kettle Reboiler Bundles

J. W. Palen, J. Taborek, and A. Yarden

1969

This report summarizes an extensive HTRI study of the boiling characteristics of kettle reboilers, including the following topics:

1. Basic theory of boiling on elementary surfaces is reviewed. A test of existing correlations against over 900 literature data points on single tubes and flat plates showed that no literature correlations were adequate to use as a basis for a general design method, and new single-tube correlations were developed.
2. Over 1000 data points were taken on industrial-size reboilers, and the main effects of pressure, physical properties, mixture composition, and surface characteristics are discussed. Important variations with pressure, bundle geometry, and mixture boiling range were noted. Present design methods were shown to be grossly conservative under most conditions, but unsafe in extreme ranges of pressure, bundle geometry, or boiling range.
3. Reboiler bundle heat transfer and maximum heat flux correlations were developed based on modification of HTRI single-tube equations to account for hydrodynamic effects of multitube geometry. Resulting correlations predicted bundle performance within about ±30%, which is thought to be the present practical limit of accuracy without actual data on surface characteristics and fouling performance for the specific fluid-surface combination.
4. Various side investigations were performed, including evaluation of effects of reboiler level, antifoam injection, and low-finned tubes (which proved to be very effective in low Delta T ranges).
5. A step-by-step method for rating or design of kettle reboiler bundles is presented, along with recommendations regarding efficient geometry specifications and operating procedures.