Thermosiphon Reboiler Driving Head Calculator
Calculate natural circulation driving head, vapor-liquid two-phase froth density, circulation ratio, and reboiler circuit pressure balance.
Reboiler Elevation & Tube Geometry
Vapor Production & Liquid Densities
Thermosiphon Hydraulic Balance
Recommended Tools & Equipment
Tested hardware and components for high reliability
Frequently Asked Questions
How does a vertical thermosiphon reboiler establish natural circulation without a pump?
Thermosiphon reboilers rely purely on density differences (thermogravitational head). The cold liquid downcomer from the tower sump has a high density (e.g. 50 lb/ft³), while boiling in the vertical tubes creates a low-density froth/two-phase mixture (e.g. 5-15 lb/ft³). The hydrostatic pressure imbalance drives vigorous natural upward circulation.
Why should the outlet vaporization mass fraction be kept between 10% and 25%?
If vaporization exceeds 25-30% (low circulation ratio), liquid film dryout occurs at the top of the tubes. This triggers film boiling, high tube wall temperatures, severe thermal fouling, polymer coking, and dangerous cyclic flow instabilities (chugging).
What should you do if the calculated net driving head is insufficient?
Increase the column liquid operating level (raising hydrostatic pressure on the tubesheet), reduce pressure drop in the vapor return riser line by eliminating sharp elbows and enlarging the pipe diameter, or throttle the liquid feed valve to dampen flow oscillations.