THE BEHAVIOR OF A PILOT-SCALE HORIZONTAL THERMOSIPHON REBOILER

Two-phase pressure drop and overall heat transfer coefficients have be en measured in a model horizontal thermosyphon reboiler operating at a tmospheric pressure and using water and aqueous solutions of methanol and ethylene glycol. The shell and riser were of glass so that flow pa tterns could be observed. The aqueous solutions produced much smaller bubbles, but neither the pressure drops nor the overall heat transfer coefficients varied substantially from system to system. Comparison of the pressure drop measurements with available correlations highlighte d areas, particularly bends and nozzles, where further study is needed to improve predictions for reboiler design. Overall heat transfer coe fficients had the expected order of magnitude (2.5-3.0 kW m(-2) K-1) b ut did not vary as expected in the solutions. Flow instabilities were noted at low qualities and explored in the water system.