Horizontal Shell Side Thermosiphons

Figure 8.4. Example of tubular heat exchangers (see also Fig. 8.14). (a) Double-pipe exchanger, (b) Scraped inner surface of a double-pipe exchanger, (c) Shell-and-tube exchanger with fixed tube sheets, (d) Kettle-type reboiler, (e) Horizontal shell side thermosiphon reboiler, (f) Vertical tube side thermosiphon reboiler, (g) Internal reboiler in a tower, (h) Air cooler with induced draft fan above the tube bank, (i) Air cooler with forced draft fan below the tube bank.

Process Conditions Kettle or Internal Horizontal Shell-Side Thermosiphon Vertical Tube-Side Thermosiphon Forced Flow... 

Horizontal Shell Side Thermosiphons 207 Vertical Thermosiphons 207 Forced Circulation Reboilers 208 Calculation Procedures 208... 

For horizontal thermosiphon/natural units the boiling fluid is almost always on the shell side, with the heating medium in the tubes. In the vertical units the reboiling of the fluid is in the tubes. For kettle units, the boiling is in the shell. ColUns suggests a rule of thumb that if the viscosity of the reboUer is less than 0.5 centipoise (cp), the vertical thermosiphon should be considered, but when the viscosity is more than 0.5 cp, the horizontal reboUer is probably more economical. 

G and H shells are used primarily for vaporizing the shell-side fluid, especially as horizontal thermosiphon reboilers. Partial longitudinal baffles force the entering liquid to flow across the entire length of the tubes and minimize the possibility of dry-out or stagnant vapor pockets. Leakage... 

Liquid distribution. The liquid distribution requirement of kettle reboilers is similar to that of horizontal thermosiphon reboilers. The techniques for overcoming liquid maldistribution in horizontal thermosiphon reboilers (Sec. 15.5) also apply to kettle reboilers. The author is familiar with one case in which channeling in a kettle reboiler was evidenced by the shell surface being much warmer in the center (above the inlet) than near the shell ends. The problem was eliminated, and heat transfer largely improved, after a horizontal baffle (which directed liquid toward the sides) was installed above the inlet nozzle.. The baffle arrangement must not restrict inlet liquid flow, as this may back liquid up in the column. In one reported case (237), such liquid backup caused column flooding. 

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