This section summarizes certain important design considerations that apply to all reboilers. Often when a reboiler fails to operate properly the cause is not miscalculation of the boiling heat transfer coefficient but ignorance of special conditions that fall outside the minimum required design procedures. Some of these are discussed in this section.

A. Fouling

The heat transfer resistance that must be specified to account for anticipated fouling is one of the most troublesome unknowns in the design of reboilers and one that requires the most engineering judgment. Some of the basic characteristics are summarized in Palen and Westwater (1966) and Taborek et al. (1972). For a more detailed discussion of fouling considerations, see Section 2.10. Since the heat transfer coefficients in reboilers are generally high, the fouling resistance specified usually accounts for an appreciable fraction of the total required surface. Yet it is doubtful if it will ever be possible to predict analytically the true fouling resistance for any particular boiling fluid with much confidence. Therefore, the only practical approach is to attempt to select equipment and operating conditions so that fouling is minimized.

A few of the most important considerations for boiling fluids with significant fouling tendencies are the following.

(a) Design for low vaporization