Reboilers are designed in many configurations, including vertical tube side boiling thermosiphons, horizontal shell side…
Reboilers General Guidelines
The following guidelines apply to all reboiler configurations.
1. The boiling regime should always be nucleate. This is assured if the heat flux is maintained at 2000 Btu/hr×ft2 or higher everywhere in the exchanger.
2. Sensible heating medium should be routed cocurrent to the boiling fluid to facilitate control without fouling. Control by bypassing heat medium results in a temperature pinch and nil heat transfer near the heat medium outlet, which should correspond to the high velocity two-phase boiling outlet. Heat medium inlet near the boiling fluid inlet promotes nucleate boiling in this region and avoids a stagnant zone on the boiling side where particulate fouling may otherwise occur.
3. Steam heated reboilers should be controlled by throttling steam pressure and should have a downstream condensate receiving vessel to keep the reboiler drained of condensate, and a vent for noncondensables. Otherwise, steam side corrosion at the condensate interface and boiling side fouling in the nil heat transfer condensate flooded region are likely.
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