Thermosiphon Reboiler Design and Analysis for Water Distillation Applications

Purification of heavy water used as the moderator and coolant of pressurized heavy water nuclear reactors (PHWRs) is a vital step in ensuring its adequate isotopic content that maintains neutron economy in the reactor core. This process is carried out in a packed vacuum distillation column which requires condensers and reboilers as essential heat transfer components. A vertical thermosiphon reboiler is used to minimize operating costs of the distillation system by eliminating the fluid recirculation pump and improving system reliability and safety by minimizing leakages and heavy water losses. This work presents a simple, direct methodology for optimizing the design and operation of such a reboiler using codes developed in-house and based on heuristics and two-phase heat and momentum transfer correlations from literature. The methodology is general and can be applied to any application requiring a thermosiphon reboiler. Parametric analysis and cost calculations have also been performed along with exergy analysis of reboiler performance.